I’ve got holes that rusted through as you could see in the pictures
that doesn't look like metal but more like bondo in that picture.
Check what the inside of the tank looks like -- use an endoscope -- can be had cheaply from Aliexpress (like under $10) and uses your phone for dispaly.
I'd sand that location a bit and confirm what material is there-- metal, fiberglass, bondo and then determine what thebest repair method is. Any of those materials can be patched/repaired. Fiberglass/Bindo would be the easiest most likely for you to do yourself. But even the metal iwth just pitted holes should not be horrific to fix Prep the area and you should be able to use jb weld or have a welder fix those holes.
Then paint the tank -- If you're going to have a welder do it, I'd strip all the paint off and check everywhere for issues -- don't want to do this twice!
REline the tank with something like KREEM ( i think that's the stuff)