The staples should hold the rubber in place. If it holds for 1500 miles it should be okay.
My concern would be how well the Gorilla Tape sticks to the rubber. I know it holds well but, will being covered with Flex Seal cause any problems?
My next concern would be the Flex Seal and how well it holds up.
I would have used rubber roof sealer and Eternabond but, in an emergency you have to use what is available.
Just inspect the roof often and watch for leaks. If it holds up then apply a roof sealer. You may get several more years from the roof.
I repaired and coated the original roof on our 96 Southwind. It has held up for several years.