So I have done a lot of work since the last post.
First, what didn't work: I caulked over the existing caulk on the belly band with silicone to match the silicone already there. It still leaked after the next rains.
Then I removed all the Trim Lock on the belly band below the window and almost to the back of the trailer. This was a real pain and required a hammer and chisel every inch of the way. There was water and water damage at several places along the way and deep areas where there was no adhesive between the two hull halves. The most water was near where I have water in the core. I ground out the bad places with a cutoff wheel on an angle grinder. I sealed all the cleaned-out gaps with 3M 4200 Marine Adhesive Sealant.
I attempted to remove the window but I didn't want to force it and ruin the gasket. There was no sign of water or water damage. After I reinstalled it I put a very thin bead of the 3M 4200 all around the window.
We just had a half-day of hard rain today and there were no leaks
To dry out the wet foam core I put a heater fan on the outside and blew it for a couple of days onto the area where the moisture meter indicated it was still wet. Some of the weep holes I drilled on the inside got moist for a few hours and then stopped. Later I put a heating pad on the inside and left it on. I will see what happens in the next month or so.