IMO, you should drop the tank, clean the hole, and install a new grommet. I wouldn't fool around with more epoxy sealer. When you say you scratched the side of the car, do mean the inside of the trunk?
The side of the car (quarter panel) was getting scratched. The metal plate on the outside that screws to the side of the body would lash back when the neck would pop through the grommet and smack the side of the car. Now, that could have been because the dummy didn't lube the gasket.
By grommet do you mean the rubber piece in the trunk? That is just a cover. Take the screws out and slide it up the filler neck so it's out of the way. You will then be able to remove and reinstall the filler neck much easier.
I mean the big circle grommet in the gas tank. I will probably go this route because it is the right way to fix it, but it may have to wait until post-Carlisle since I don't have the time right now.
Would appreciate any specific recommendations on how exactly people got the grommet in the gas tank hole and also what specifically was used to lube the grommet to get the neck through.