Gas Tank Rust

BB's, drywall screws, anything loose is gonna get trapped in that recess. If I ever have to do this again, I'd use something like jack chain and make sure I had access to the end of it. Vinegar sounds like a much better idea.
As for the rust, it's still there 10 years later, no worse, no leaks. Frankly, I think the liquid and vapors in the gas are preventing any further progress in the rusting process, and my ridiculous shenanigans were the result of a pointless exercise to address a non-problem.

If you keep the tank full, there's less chance of rust advancing than if it were half-empty. The main thing is to stop deterioration that leads to leakage and pull the petcocks once in a blue moon to make sure they're not getting clogged with rust particles. The Evaporust chemically changes the rust to a different kind of oxide that can't grow because the chemical that's oxidized is no longer present when the solution is drained out and the tank dried.

The Bill Hirsch Kit I used on the Titanic comes with a cleaner solution, an etching solution ( similar to Evaporust, POR-15 and other recombinants) and a compatible sealer which is supposed to be used very sparingly as long as all surfaces are coated. Proper application is everything, so we'll see how well I was able to make it work.

For decades I used Drygas (isopropyl) to purge the water from my moto tanks (and sleds, ATV's, power equip, cars) and stop bottom pinch weld rust through.
The only silver lining with ethanol blended fuel is we no longer need to use drygas.
Also, off season storage includes a few oz.'s of two stroke oil along with the Sta-Bil to coat everything with a corrosion resistant film. Works great.