I think I’ll put a new fitting on there and put the fuel back in right at a quarter tank and see what happens…

 

I was going back through things and this picture caught my eye. I've circled the exposed ferule because I'm confused as to why it's that color. I'm assuming the fitting is stainless steel but I'm questioning whether that ferule actually is. The trick about SS is that it is in fact stainless, the name kinda gives it away. So if it is SS what the hell has been in that tank that will turn SS that color? If it isn't SS then what the hell is it?

The other thing I circled is some discoloration on the tube. It could just be from when the level gauge was spot welded to the tube, but I remembered you were getting some odd behavior from the gauge cluster. So could be a short that's been arcing to the tube there. Worth a look anyway.

I also see rust or corrosion on the level gauge bracket. That brings us back around to the whole SS being stainless thing, so not sure what's going on there.

 

Just came to me. Electrolysis could probably do that to some grades of stainless. It's just a guess but it is somewhat plausible.

 

I took some pics. One of those sensor wires has a splice.

 

I took this video. Don’t know if any of this matters but just thought I’d share.

 

Crap, look at the rust on the ground wire connection. That alone could be throwing the gauge reading out of whack. Probably want to go after that with some emery cloth or wire brush before putting things back together. You want shiny metal touching shiny metal when it comes to electrical connections.