I seem to have a knack for destroying my black tank

Slight update. I finally decided to go the Plasti-Mend route (sorry no pictures) I applied about 5 or six coats overall and then buttoned it all back up again. I'll hopefully get a chance to test it all out soon and I'll report back as to whether or not it leaks.

the Plasti-mend does seem to dry hard and it possibly melts into the tank. Unfortunately there is no real way to know if it's actually melting into the plastic or not without cutting a hole in the tank.