Hi,
1) The sound ohm or variations of that sound is good coming and going, in or out, visualized, breathed, felt or spoken. The effect of engaging with the sound, in the sense of it as spiritual energy, is present in both the in and out of a cycle of breath,even if you are specifically expressing it, on just one or the other. Whether it is expressed out loud, or felt as a physical vibration, or visualized, the common denominator is you, engaging with spiritual energy, that energy being present, and you working with it.
2) Starting with the three breaths is a cleansing, relaxing, and release technique, as well as bringing you into a more focused or meditative state. It's good anytime you start your qigong, active or inactive. The mouth is an opening. Extra energy, tension, can go out with the breath. You then close the mouth, or that opening, and begin a different work, and keep the opening closed. Your eyes gaze downward, and are also an opening.
I utilize that too. You can intend, deeper release in these beginning breaths. In the end of an exercise or meditation, it is more about coming back into the physical body, and sort of makes a bridge, to then harvest qi.
3) Don't be concerned about losing your place in SU. Bottom line, you can start again anywhere, with either sound in any place. The only important thing relative to this is finishing your meditation in the lower dan tien. Don't judge your performance of SU. You get into the flow, you can come and go,,,,no harm. The sound, as I said in another post, is spiritual energy. It is more or less one word, one sound, one energy, expressed two ways. Again, there is not right or wrong. If you are listening to the CD, just relax and go with wherever you are at. If Master Lin finishes before you, just move forward to the lower dan tien to close at the end. You can do that finishing out at your own pace, or just fast forward to the lower dan tien and close. Try to keep the whole of your session relaxed, with no self judgement on how you do with it.
4) There is no set way. I usually do as you do. See them periodically during the time period. You don't have to, but that is fine to do so. It is best, to invite them in, and , make a point to send them off. See if you notice a difference in how you saw them come in, and how they looked when they leave. It is good to see them off and have that separation at the end. If you recall them later, after forgeting, proceed at that point to see them off. Again, no harm. You will get better about that.
5) No comments here on my part! Be creative. Whatever comes to mind.
love,
gallen