Finally got going with the tank. I scrapped off the rust
But a LOT of the paint came off and started to show rust that I couldn't get to from the front. Started to think about having someone do it. My mechanic came and took the tank, that gave me easy access to the front side of the basement that apparently has had the protective spray worn off and rust formed.
I took the opportunity to spray Rust Reformer on the freshly scraped metal while the tank is out being repaired. I may even decide to put more undercoating on before taking the RV back out in the world.