I chipped my 75 much worse, in my case I used a larger bulkhead and drilled the hole out. If your sealing effort doesn't work give that a try, worked for me. Ended up going to 1.5 inch for the return then just had a reducer right in the bulkhead to go back to 3/4.
I always put tape on the back of my glass to help prevent this, and I use almost no pressure for the last little bit, I mean I let it take forever, the last bit takes longer than the whole hole. I've also been known to drill both sides and meet the holes in the middle, but I don't think that's required and it is harder.
Whiskey