Welcome here! Good luck with your search!
1. Weak points are (but not limited to...) axle
(sag), frame (severe rust or cracking) and body integrity (sagging door).
There are a few other threads that cover this issue, and this helps too > Fiberglass RV - Document Center - BuyersChecklistFiberglass RV - Document Center - BuyersChecklist
The more systems you have electrical
, plumbing, etc.; the more problems there may be. There are a huge amount of resources available here for problem solving though!
2. My 1998 Subaru Forester sags quite a bit with our Boler
around 170lbs). I just learned to live with driving 'uphill' all the time! There are quite a few people here who use Subaru's. I don't think airbags are available for Subaru's. Maybe there are more options.
Also, there are a number of Oregonians who might be near you so you can get a better look and feel for the trailers before jumping in. Maybe you can visit a gathering!