Are you saying you tried applying it twice, or just once? If just once, hell, try again. You should not be having such issues, but just in case you are, a battery pull might not hurt.
1: Sure. Or you can get the files from Pete's site as well, although if I were you I'd stick with P3's from the site you linked to - IIRC, it already has Busybox, which Pete's does not.....
2: Well, since FRG22 is what the OTA is going to, probably not - but there is a small likelihood that *everyone* will get a notification for the final 2.2 OTA, b/c I was running Pete's BB 0.4 and *I* received the notification for the 2.2 first OTA last week.
For future OTAs, you should receive notifications.
3: There is a whole school of thought on how you don't need them and I tend to agree - however, I keep one installed b/c 1) I bought it, and 2) for those Justin Case moments (sorry for the play on words).
Android is pretty efficient at managing your memory, and killing apps that automatically load actually slows performance, b/c temporarioly your phone is faster while you're doing something, and then it slows again as it continues to do what you're trying to do *and* starts re-loading those apps that were running in the background. If there are apps you don't want running at all, you're better off uninstalling them.
If they are system apps, like Corporate email, then you're better off learning how to root and removing them yourself so they won't auto run.
Another theory would be to look into AutoStart apps and configuring those, if possible (never tried it myself).
Ummm, no, b/c Facebook is an app that you install from the market - and the last two updates from market were made this past week. After this version was already primed and readied for release.