how to remove a bolt stuck in the tank

Pretty much need to spin it out of there, then clamp the fitting and get the bolt out. Then clean the hole in the tank and use some epoxy to secure it and some anti-seize on the bolt threads.

^^^ What he said.

Electric impact. Spin the crap out of it while pulling on the shroud. The plastic will get hot and the insert will eventually come out. Get a new insert and clean the hole out.

I took my tank and insert to a body shop friend and he used Panel Bond on the insert. Said it would never come out.

I usually heat the bolt up with torch (carefully) and pull straight out. This minimizes damage to plastic. Then you can use a soldering iron and little pieces of plastic off an old fender.etc to refill & shape hole. Then reheat brass insert and push back into tank. Done it quite a few times with success............I usually put some water in tank while working around it with torch just to be safe..........

I have spun it with a screwdriver under the bolt putting outward pressure so it spins out. Free up the bolt and insert and clean it so the bolt goes in and out. I use a soldering iron with a wide flat tip and melt plastic back over. I have used an old fender for more colored plastic.