I filled all the gaps on the corners with silicone to seal it and to hopefully resist thermal bridge where the aluminum angle was exposed. Then I painted the sleeping compartment; mostly to seal the wood. I am going to install foam insulation panels on all the walls. The panels will have the foil side towards the wall with an air gap in between. I'll install some wood slats under the panels so I can lean against them when I'm sitting up in bed.
I figured out the layout. I have a full size 37 inch spare under the bed. I'll mount a second on the passenger side. Behind that will be some storage boxes for lighter things. The toilet will fit next to the wheel well. The camp stove will be on a shelf by the window.
On the driver's side I will make a stand that bolts to the truck bed to hold the fridge. It needs to be up high so I can squeeze the second spare out from under the bed. I cut out a piece of cardboard with the footprint of the fridge to help me visualize. I would like the fridge lower, but this is the best solution.
Mounting the spare and fridge to the bed will transfer that weight to the truck and not the shell. Under the fridge will be a spot to put the floor jack and tool bags. I will also have more storage like on the other side of the truck. This keeps the largest open area in the middle of the truck bed. It's important to be able to have a spot to change clothes, throw things in the truck and carry large items temporarily. I have never understood how people can travel in teardrop trailers. Do they climb in with wet clothes and then try to change while lying down? Yuck.
This leaves half the bed under the sleeping compartment open. I'm thinking putting a water tank there. Then I need to find some place to put a sink. At least I am finally making progress.