Good thing you didn't put your money down.

The seat-post is almost bottomed-out in the tube. Only 1/4'' or less space remains at the bottom of the tube by the seat-post. So that isn't what caused the crack.
I don't know what caused the crack, but it's there.
Your suggestion to reinforce it with fiberglass, was something I hadn't thought of.
I'll try this repair out and see how it goes. Then post the results.
Thanks for your suggestions/advice...

PS, I was born and raised in NYC, I know what your saying and agree.