Side Molding Issue

[Freestate]

I've got an issue with the side molding on both fenders. The molding bracket by the door keeps popping out. I found out that the person who installed the molding didn't put a locking nut on the back of the bolt (see pictures). Any idea how I can get behind it and put a locking nut on, or fix it the right way without taking the door off? I've tried almost everything and can't seem to get a wrench or my fingers back behind the fender.

Also, I've noticed that a lot of the molding is pretty loose. Any suggestions on how I can fix this? 3M tape? Can this be done without taking the molding completely off?