seems like every time there's an issue with cracking or warping its rubbermaid coolers. i bought two orange igloo round coolers when i first got started. realized i didn't need two as i just used my second pot for sparge water. not one issue of warping or cracking in my igloo, and i will use 185F sparge water.
if you don't want to get another at this point, you could drill a small hole in bottom, squirt in some adhesive and then put something heavy in bottom over night until adhesive dries. then fill the drill hole with epoxy or other plastic filler.
short of that, you may want to get that new cooler.