Technically, you are supposed to fuse the wire every time it drops in gauge size, so any transition point where the 0/1 splits off into something smaller a fuse should be in place that is adequate for the smaller wire size. That being said, there isn't much of a chance of anything bad happening if the lower gauge wire is only a couple feet long between the distribution point and the amp. Just use common sense with that. A bolt will be fine for acting as a distribution point, but make sure it's well covered. I can almost promise you that at some point you will ground it out on accident if you don't.
For ground the shock tower bolt will probably
be better. Anything that connects to the frame is better than just a body connection (like the sheet metal floor). There's much less resistance that way. Make sure to do the Big 3 as well.