Welcome. Here are some of my thoughts:
1. GEO Method. Search the forum for really good discussions.
2. Yes, I always have. Its necessary to check and caulk the seals.
3. Dicor LAP sealant or the equivalent Alpha sealant. Self-leveling for the roof.
4. Not sure with your year Roo.
5. The sensors are notoriously inaccurate for any trailer. They easily get gunked up. No one I know has cleaned them, but you can replace with a better sensor. I personally haven't done that but it is an option.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD