We have a two step ladder with a big handle across the front/top so he can hang onto it if he feels nervous and I can also tell him to put his hands there if I'm doing something dangerous/he has wandering hands.

Being exposed to how to handle knives is really good stuff! Be consistent and he'll pick up on it.

Part of the reason dull knives are dangerous is not JUST the "needs more pushing" but ALSO a sharp knife will cut skin/fat/muscle/tendon/nerve cleanly while a dull knife will mash and mangle. If you're trying to put your hand/finger back together you want a clean slice, not a mashed up mess.

I like the idea of the tower and I know a few people who have them and love them. I'm pretty sure that even if our kitchen were larger I'd break my toe(s) on it, though.