Hey Eric,
1. Noting is better. Scanning is good to understand what "dissolution" is, since you get to see it happening all over the place. Noting is good to notice specific characteristic of the way experience is presenting itself. Particularly you should be looking for impermanence, non-satisfactoryness and no-self. Impermanence you know what it is, non-satisfactoryness you'll know when you see it (it sucks really bad at first), and no-self is when you realize "heh, there is no-one commanding the ship, intentions and mental dialogue and etc all arise of their own accord," and it will feel really strange not having the sensation of controlling what you decide to do.
2. If you are in this for the enlightenment thing, there is no reason not to go for stream-entry ASAP, except maybe, just maybe, you didn't decide to do this thing fully heads on with all you got no more doubts at all. When you do, you should find that progress will come (way more) rapidly. You are likely already very much on the ride, given you got A&P like experiences in the retreat, so now is the time to run to the finish line. If you are having difficulty focusing and having a hard-time dark-night like thing, then you could very well reach escape velocity, go for stream entry, and then get tired of the whole path thing, and go for arhatship.
3.
Eric:
In terms of noting, when I have tried it, it seems like my attention jumps from sensation to sensation on the body faster than my mind can mentally classify and note each sensation. Should I just slow down my attention and only note one or two things per second until my mental verbage speeds up? What's the way to do this?
Noting is the activity of really going down all those filters and "touch" the sensation in the way it really presents itself phenomenologically. It isn't looking at the sea and thinking "sea," it's diving into what and how the image of the sea presents itself to your mental apparatus. So the important part of noting is this "touching" of the sensation with your bare attention (and doing this you will find that the sensation is impermanent, unsatisfactory and not "you"); the actual verbal classification is more a device to make sure you are actually doing it right, and stay on track; it comes after the actual "noting." So you see, you can be "noting" 5 times per second or more, while at the same time only "noting out loud" once every few seconds.
Hope that helps, and take care,
Bruno