My detached garage has a roof section that is a VERY low-pitch metal
roof.
Low, as in probably less than a 6' rise in 45 feet.
The metal panels are installed over tar-paper over plywood.

The metal panels are long enough that there are only 2 required for the
run down the pitch.

I'm getting consistent leaking across the roof at the 1st plywood joint
that's below the panel joint, most of the roofing screws at the joint
have their washer deteriorated and hardened, and some have been leaking
long enough that they are loose from the plywood rotting.

The amount of plywood that is rotted is limited to a small strip
running across the pitch, and only around the screws, and I am not
going to strip the roof to replace it.

My plan is to get new screws, and replace the screws where the wood
will hold the screw. Where the wood won't hold a screw, I plan on going
a little up & down the pitch (a few inches) and putting in a screw.

My question is, for the spots where the wood won't hold a screw, should
I put a bunch of roofing spooge on a new screw and shove it in the
hole, or should I fill the hole with silocone or roofing spooge?

Also, what is the likelyhood that water is migrating backwards up the
lap joint?
If its likely, should I raise the top panel slightly and apply roofing
spooge between the panels, or should I just apply some spooge over the
top of the joint? Ditto ques. for sealing tape (which I hope was used
in the 1st place...)

On the day I was on the roof, it went from sunny and 55 degrees to
cloudy, rainy, and about 45 deg., and I could see the panel joint move
by about 1/4 inch.

-Dave