1. For me, and because I bought the Classic version first, I'd suggest the boxed edition if possible. While I first started using Basic way back before PCs, having the manual for DB next to me has proved itself invaluable. Sure, the on-line help has most of the same information, but it's harder to "flip through the pages" in the on-line help when you're looking for something.
2. Well, I don't know. It really does depend on if you have any previous Basic experience and are the kind of self starter person to pudge around with things until you understand it. According to the forums there have been mixed reviews on the DB book, mostly because it's for DBC (my version) and not Pro, so some examples don't work "out of the box." When learning, it'd drive me nuts to have to keep converting code into Pro from the DBC just to get the samples to run.
3. Well, judging from my experience thusfar (I've only used DBC a few months now) I think it could make a good rts, but the host machine might need to be pretty advanced. Some of my friends who have older units have complained my compiled code runs a little slow for them, but that can be adjusted somewhat. Granted, it's not as fast as C for example, but a heck of lot easier to code imho.
So there's my two cents worth, use your best judgement.
S.
Any truly great code should be indisguishable from magic.