1. You could drill the tank instead of using hob or wet dry. That's how most of the frag tanks I see are done
2. This depends on what kind of things are going into the frag tank. If it's only frags I'd just to egg crate and not use sand. If you're going to be growing out some bigger colonies, brains, scoly's, etc then I'd also incorporate sand.
3. Same as your normal tank