Gorilla makes a bunch of different glues. I second the idea of testing out any solvent at home. The “cleanup” solvent may not be the same as a solvent for cured stuff. you may also have lucked out. Several Gorilla products require the glue surfaces to be wet. If your protege didn’t do proper surface prep the glue might not have bonded well and might chip or peel out better without solvent if you can get hold of an edge. If that’s not the case, I’d think hard about whether your correction will actually make the situation better. good luck.
I think from your description you have 2 options. depending on if you think the hold should stay and you just don't like the unsightly glue job. Or if you think its dangerous and needs to go for safety.
1. Use paint or some kind or adhesive and some dirt to camouflage the glue job. This assumes the hold is essential and also that the glue will hold.
2. Remove the glued on flake and scrape or peel the glue off. This changes the climb but that's what happens when stuff gets loved to death.
You described the flake as being 100lbs. Even glued on this thing could be an unseen danger to climbers and belayers. It might be safest to just rip the hold off.