Just a quick update before I crash.
The sump repaired fairly well, there was a 2x4" patch where the two sheets didn't meet, I put enough PVC cement to fill the gap and held it down for 5 mins as it hardened, seems to of worked well. Hopefully there isn't a risk of failure because of the gap filled with cement.
The sump has held water for 2 days now, and I've just finished plumbing the tank (major PITA.)
Didn't overflow when I killed the power, so far so good.
Thanks for the help!
If I get enough motivation I'll snap a few pictures of my piss poor plumb job, still need to recover after scooting a 75 gal with 100lbs of sand and a half foot of water and the fumes.