Of particular importance and concern is the meaning of parimukham in the context of satipatthana practice in the stock phrases that accompany going to a forest, foot of a tree, sitting cross legged, and parimukhaṃ satiṃ upaṭṭhapetvā.

According to Anālayo, this term can be understood both literally or figuratively.
literal would mean: mouth/nostril area, or area generally around chest and front of the body
figurative would mean: making sati the main priority (parimukhaṃ satiṃ upaṭṭhapetvā.)

As Analayo points out, both literal and figurative interpretation make sense in the context of anapana, but in the other occurrences in the pali nikayas, such as brahamavihars, abandoning hindrances and contemplation of bodily postures, literal interpretation would not make so much sense.

evidence in favor of literal interpretation

see dmytro's posts in this msg board thread  discussion thread with lots of info of case in favor of mouth/nostril interpretation

evidence in favor of figurative interpretation of parimukham

There are quite a lot of evidence showing that jhana does NOT start out with focusing on a small area:

1. The Parimukha expression in Chinese is translated as "bringing mindfulness to the present" or "bringing forth mindfulness" (xinian zaiqian).

2. Thanissaro Bhikkhu pointed out the earlist passage where this expression occurs--in the Vinaya. There, it is explicitly defined as the whole frontal region of the body.

3. Focusing on such small areas like the nostril and the mouth is fundamentally at odds with the nature of the satipatthana practice, which is always about knowing activities within an experiential domin in its entirety (i.e. body, feeling, mind, and all of the above within the frame of Dhammic categories). And the parimukha expression most often occurs as the precursor to satipatthana practice.

4. In the Dhyana-samadhi sutra (Zuochan sanmei jing), that expression is explained in detail as "bringing forth mindfulness so as to infuse it in the whole body, from toes to the hair, and throughout the pores, like wind would traverse unobstructedly through the eyes of a fish net."

Bhikkhu Analayo, on p. 128-129 of his book on Satipatthana, says that the Abhidhamma discusses parimukham as if it exclusively relates to a precise anatomical position, when in fact there are a dozen sutras where it obviously refers to an injunction to bring attentiveness to the practice of mindfulness (the figurative meaning of parimukham is “bringing something to the present”). These are the suttas in question: M I 219; M II 139; A I 184; A III 320; Ud 21, 42, 43, 46, 60, 71. Note that if you read parimukham as mouth or nostril, it would not work in the contexts of all those suttas.

Rhys Davids, the first English translator of the Nikayas, has this as “setting memory in front,” as in the sense of bringing mindfulness (memory) to the objects of one’s practice (anapanasati)—i.e. to keep in mind that the task at hand is the anapanasati practice

Bhikkhu Sona, the monk who writes about how jhana nimitta is a Visuddhimagga invention, says that the parimukham expression means the “embracing” (pari) of the entry point (mukham) into the practice of anapanasati.
Patrick Kearney has it as “completely (pari) facing/encountering (mukham)” one’s experience, in the sense of being face to face with one’s anapanasati practice.
Now, onto your questions:
The Dhyana-samadhi sutra translates parimukham as literally mouth-nose (koubi), but in the context of whole-body awareness and not in the context of locking the mind down onto mouth-nose. "Koubi" is the Chinese equivalent to parimukham.
There are Sanskrit, Chinese, and Tibetan sutras (especially the latter two) that elaborate upon not just step 3, but other steps, too. I only cited the Dhyana-samadhi Sutra because so much controversy revolves around the fundamental modality of Buddhist concentration--whether it is similar to the Hindu practice of staring at or fixing the mind at a stationary object like candlelight or the third eye, or that of satipatthana. The reason that people like Culadasa believe that the Buddhist jhana is not something uniquely Buddhist, and is in fact a pan-Indian practice (Chinese: gongwaidao--shared with the non-Buddhists), is because they understand Buddhist concentration practice is of the former modality--attention fixed at a stationary object.
The Dhyana-samadhi Sutra does NOT go on to explain all 16 steps. One has to look into independent texts to look for disparate clues. There is one version of the SA, MA, DA, and AA, respectively, in the Chinese canon. But what makes the latter unique is that (and we're only focusing on the non-Mahayana texts) you have these independent sutras of different sectarian persuasions (e.g. Sarvastivada, Dharmaguptika, Sautrantika, Vaibhasika...) that, together, give you a much more trans-sectarian, trans-geographical, and trans-temporal purview of the nature and evolution of Buddhist meditation. In fact, the early para-and-post-canonical commentaries preserved in Chinese contain the most detailed instructions on jhanas, which depict a starkly contrasting picture to that found in the Visuddhimagga. Examining these sources with a sensitivity to their chronology, one can arrive at a compelling sense of how jhanas have changed over time, as well as much more nuanced and technical ways of developing jhanas.
Some of these independent texts are earlier than much of the Pali Nikayas, while some are later. In the case of the Dhyana Samadhi, it is a later text, and in fact contains some nascent and proto-Mahayana themes. Many of these "non-Mahayana" "sutras" in Chinese are composite texts--the translators culled and mixed passages from different sources to come up with a primer intended for their specific audiences. And so we have some pretty interesting Chinese sutras where parts are very early, and parts are very late; or parts that are extremely relevant to meditation, intermixed with parts that are wacky and heretical.
Nonetheless, the passage in question, read in conjunction with other passages and sutras, provide us with a compelling alternative to reading "whole body" as "the entire duration of the breath." The latter, in my view, severely restricts the way the 16 steps are to be developed. I agree with your sentiment about not having problems with abandoning certain practices at some stage of one's practice. But in my very subjective experience of working with students (many of whom had had zero background in meditation), Thanissaro Bhikkhu's approach (assessing and making comfortable one's breathing by varying, among other things, the lengths of the breath) to steps 1&2, for example, is so much more conducive to the development of the rest of the 16 steps. It follows more naturally what the Buddha teaches about what to do in everyday life, and it transitions more naturally to the rest of the 16 steps, all of which requires sensitivity to one's technique, and not just laser-like concentration.
It's undersandable that we can get flustered about the confusing array of interpretations. But there's actually so much to be thankful for. You know how historians can't be sure of what happened even 50 years ago. For some uncanny reasons and stupendous luck, some of us can sill benefit tremendously from teachings that originated 2500 years ago! I'm going to focus on being grateful rather than frustrated:)

strong evidence from Agamas says parimukham not referring to mouth/nostril

Even though the earliest pali literature would favor parimukham as "nose/mouth region", many examples from the parallel Chinese Agamas which includes even more schools of early Buddhism than Pali Nikayas show that parimukham is meant figuratively as "establishing mindfulness as the primary focus and main priority" similar to the English  expression attending to "the task at hand" does not mean we should focus our attention at the spatial location at our hand. 

(from correspondence with friend)
Yes, the Vibhanga section predates the relevant Vinaya passage--the Vibhanga was the work of the Vaibhasikas who were active in the BCE's.
However, the evidence that parimukham does NOT strictly or primarily mean nose-mouth is overwhelming.
In addition to the dozens of examples Analayo cited where parimukham does not mean parimukham, the Chinese Agamas offer even more irrefutable instances.
For example, take a look at the first sutras of the linked Zengyi ahan (Ekottara-Agama The first sutra is about recollecting the Buddha's virtues. Parimukham here is clearly explained as meaning "bringing attentiveness to the task at hand." You simply do not recollect the Buddha's virtues by staring at your nose!
The second sutra whose topic is the very definition of "mindfulness": "mindfulness" here is tautologically explained in terms of parimukham--"bringing memory to the fore." In fact, does it make sense to say that "mindfulness"=fixing the mind at one's mouth/nose? And the sutra clearly states that parimukham means establishing the presence of mind.
Sutra number three: how to recollect the virtues of Sangha? By virtue of "xinian zaiqian," or bringing to the fore of mind the qualities of the immaculate Sangha! In other words, parimukham in this case, once again, cannot mean staring at one's nose.
Elsewhere in the Agamas, parimukham is often paired with the expression "zhengshen zhengnian"--how do we "establish the proper physical posture and mindset"? The sutras ask rhetorically. "By bringing to fore mindfulness [over one's posture and the quality of] mindfulness." There are numerous such examples in the Chinese Agamas.
Sure, the Vibhanga might predate some portions of the Sthiravada Vinaya, but what about the overwhelming numbers of suttas? Mind you, the Chinese Agamas, unlike the Pali Nikayas, contain sutras from Sarvastivada (which includes Vaibhasikas, the very school that composed the Vibhanga), Dharmaguptika, Mahasamghika, Kasyapiya...sources. There are also independent texts that came from still more sectarian sources that are preserved in Chinese.
Virtually all of these suttas do not agree with the Vibhanga-Patisambhidhamagga-Vimuttimagga-Visuddhimagga model (the commentarial tradition, which by all indications represented a discontinuous tradition from the sutta lineage. This particular commentarial lineage has been influenced by Hindu notions of what is concentration--staring at some stationary object). If these sutras from different Schools overwhelming agree with one another, that can only mean that their understanding of parimukham came from a pre-sectarian early nucleus/template that predated all Abhidhammas and in fact all the Nikayan suttas!


analayo's satipatthana book page 128 contains good summary and references of parimukham  discussion thread with lots of info of case in favor of mouth/nostril interpretation

related topics:

tags: parimukham