I don't know, Steve. Surprisingly, there must be some cases where USB booting works. It's news to me, and to the guys at Apple I checked with, but there you go anyway. Clearly, there are problems with it in many situations, so I definitely wouldn't rely on it. (I thought perhaps something had changed in some brand new hardware, but that's not the case here either.)
Anyway -- to get to your questions:
1. It depends, of course. I do regular backups, and run from a Safety Clone, because I install a lot of stuff that could mess up my system. A backup, once restores, restores everything -- including your user files. So, if your backup is a day old, and you need to restore it due to a badly behaved new driver, app, or whatever, you lose a day's work.
With a Safety Clone, you just boot back from the original volume, and lose no work.
2. Yes, it's not a backup, it's a checkpoint of the system and applications. It's not designed for that kind of recovery -- that's what your backup is for.
3. That might be a psychological condition, for which you'll have to seek professional help.
(Glad to hear it, though!)