So sorry for your issue.I watched your video, and here are just a couple ideas. You could cover that whole radius area with a long strip of eternabond tape. You can get it in 6 to 8 inch wide and run it down both side's of the rig. Another idea is how the dealer actually does a repair. I copied this from another forum and it is how the dealer fixed a fiberglass roof. This was a repair about a 1/2 foot long.
" The tech cleaned the area with non-petroleum based solvent then filled the 6 inch crack with fiberglass resin, then he cut a patch of fiberglass sheeting of the same color and used Marine 5200 vulcanizing adhesive to apply the patch. It bonded to the roof as good as new. He used a heat gun to make the patch soft enough to form to the radius of the roof"
Or tear the whole thing off and put a Flex Armor roof on it.