Redrill the loose fittings, use a larger size screw, (#10), make gaskets from shower pan material, available from any big box hardware/home store.
What's wrong with the lower portion of the ladder?.
It's only aluminum tubing, (you can substitute 1/2" electrical conduit) and steps are readily available from lots of RV supply houses. If you don't have one, pick up a conduit bender, and , with a little hardware fasteners, there you have a new ladder. Depending on what is wrong, you may be able to repair your original. Either way, you're good to go.