1. Probably normal...samurai front springs set flat from the factory...rear springs usually have a little bit of arch to them, but not much.
2. Yes.
3. Probably 31s, maybe 33s, if you gear it right.
4. Probably either the sending unit in the tank, or a wire burnt/broke in two in the instrument cluster. The temp gauge and fuel gauge uses a common wire. If you open up the instrument cluster (you need to completely remove it from the dash), there are some hair thin wires on the back of the fuel and temp gauge....look for one of these being burnt/broke in two.