This has been brutal.

It turned out my gamble paid off, and the return line I ordered was the correct one. My car is running!
Now to just let the gas run out again so I can drop the tank one more time. It won't be a long wait. The valve is leaking despite my repair attempt, so I'm gonna try one more fix (with JB Weld this time) before admitting defeat and ordering a new tank.

I need warm weather and my motorcycle. I actually enjoy wrenching on that... Lol