home depot sells some stuff...Naval Jelly or something like that, its in a white plastic bottle (like a 1 pint bottle) with a purple label, with all the other cleaning stuff next to the paint. it will dissolve rust. So might want to try that and then spray over the now bare metal with some sort of a primer in a can you can get at autozone. of course if this doesn't work you'll have to replace the tank.

As far as the hose....cut the ends off of it, replace with some fuel line hose and 2 worm gear clamps (the clamps that have the screw that you turn to tighten) from autozone and you'll be fine.