i have used heat guns for bending alot of acrylic into some hard angles. it can be done with time on your side. i have never had any problems or burns or bubbles.
i would remove the bottom glass and put in new non-tempered glass. that way you can drill it if need be.
just use aquarium silicone or any other that does not have anysort of mold inhibitors that could leach into the tank water.