[GoaterAz]

I'm far from a mechanic but I do have a welded in roll pan and my tailgate was rattling over bumps, after inspection, that same lower bolt you're referencing was only finger tight. I don't see a way of accessing it with a tool without cutting or clearance from either outside or under the truck (again, I'm far from a mechanic and have limited tools lol).

Not sure what you're running into, but I noticed they sold tailgate rubber bumper stops and my truck didn't have them, I bought some and it completely eliminated the rattle, the tailgate closes nice and tight.