[RMcNeal]

Slide seals should normally flip outward as the slide comes out. As they age, they get brittle. You may need to moisturize them and clean them up. I use 3in1 RV Rubber Care. It comes in a spray can and you can spray and wipe them with a micro fiber cloth. Don't use anything with petroleum products. It will break down the rubber seals faster.
I don't see any cracks in the roof in the picture. In general, clean the roof with a mix of water and dawn dish soap. Any cracks in the caulk around objects should be cleaned off and resealed using Dicor or something similar.
As for the rear damage, if you can push it back together and reseal with silicone, it may be OK since you're not moving the trailer, but I'd try to get it back together first. Eternabond tape will seal to keep out water, but it won't be pretty.
Not sure which light you are referring to on the right front top. Is it a red clearance light? They should only be on when the tow vehicle is hooked up and headlights are on.