His biggest mistake was in not hitting Gotti.

Gotti was going to move on Paul (basis Ruggiero being caught on tape moving H, which wouldve condemned the crew) irrespective of whether Demeo was alive or not.

Gotti knew it was kill or be killed.
Paul didnt.

Though Pauls future was bleak with an almost certain conviction and life sentence in the commission case. So either way, he was on the way out.

Personally I'd take the bullet.