If I am looking at that correctly using that plug then dropping down an inch to a 2" diamiter pump is going to put that pump below the diff.
That is a no on safety in my book. Thats actually saying something. I would drive something with only one wheel to stop before running a lowered car where the fuel line could be ripped free. I have scraped tanks over speed bumps before in lowered rides. It is not something that you do twice before fixing the issue or installing protection.
Your left with raising the tank, installing a smaller tank, or installing an in tank pump.
I would go with an in tank pump here.
Panel bond is amazing stuff. My money is on the gasoline breaking it down over time though. You may get several months out of it sealing. But eventually I feel it would fail leaving you with a slow leak that would quickly turn into a larger one.
Get an in tank pump.