You've done your due diligence by inspecting for any water damage inside, has no smell, and from the pictures you've shown, looks like someone or the factory
really slathered on the sealent.
IF...you can get it at a really good price, using the roof as leverage, I'd suggest you scrap off all that caulking with a plastic scraper and replace it with Eternabond tape. Then you'll never, or rarely ever, have to worry about leaks again.
Here's my ad free blog article covering sealing the seams in a Class A that might give you an idea of what I've done with mine that you could copy. Note that all RVs face the water leak issue (mostly):
Roof and roof work...
Of course there are some seams on a TT that you wouldn't want Ebond tape on but you'll work it out I'm sure. But they make it in different colors too. Including black.
Here's the brochure for that rig...note they do a pressure leak check at the factory:
Cat Brochure