[Chuck Sea/Tac]

The tank wont fall through. It’s paint bubbling from most likely, gas drippings. It will have to be repainted. Not sure of what’s involved, like does the tank need to be pulled.
You should run or drain tank below the gas gauge glass by several inches. Buy a gas gauge removal/install tool kit. I would probably just buy the whole linkage kit. You do not want the cork float, you want the neoprene one. Several years ago, when I upgraded mine, I had to do a little innovation to get the neoprene float on the linkage. Don’t know about now.