Yes, pin holes in the pick-up pipe can be a problem and not easy to test it. Mastic or butyl tape for the seal to the body. Better than caulk from a tube. Make sure the filler neck to body seal is good, replace is suspect. New connector hose and breather pipes. Make sure the breather tube in the outer filler neck is clear.
If you have a pin hole or holes in the fuel line from the tank to the pump that can also suck air. Again, these can be hard to spot and may well be on the top of the pipe and so not tending to show a leak. If there is a lot of underseal over everything it may show as a small darker/wet patch.
Fuel gauge sender needs a good earth. Mastic seal can make for a poor one so adding an extra wire not a bad idea.
Not as easy as swapping the tank on a saloon. A jack and a 20" x 20"-ish piece of thick plywood will help with removal. Good luck with it from another Wagon owner.