DD69. You asked for suggestions so...if it were me(actually it was at one time) I'd shave the rivets for the bottom trim and just forget about putting it back on. I really like the way they look but they are so problematic with rust issues that they aren't worth the hassle. IMO.
The rust issues in your window channels will never go away until fixed correctly. Only by removing ALL the bad and replacing it with good metal will you not have to worry about it again. That's where the good money will be spent. IMO.