JB Weld
has a water proof expoxy putty, i have used on a variety of things
including a leaky A/C on my first class A, that leaked water in the rain
it is so water proof, it cures in the rain or under water
it would be my goto for those screw holes
clean both inside outside and in the hole
roll up a little like playing with 'clay'
push it in the hole , and squish it on both sides in and out
mushroom style like a rivet
once its dry (24 hrs ?) paint it or seal it with anything you like
JB water weld
i try to keep a tube on hand, great for leaky water lines
just turn off the water pressure for a few hours, to let it set up