Im hoping im not opening myself to liability but I first put the tank over an exhaust pioe of,a fast idling car and pump gas into the tank. The fumes get rid of all the volatility out of the seams.
Even a tank that has been empty for years could give a problem.
I always remember a scrap metal yard In rozelle where a guy got killed oxy cutting the tops of old 44 gallon drums.
Trev hopefully you have done something like that or you are really lucky.
Re your pin holes ibe never had any luck filling holes up with the latest miracle product.
Just pressurise the tank with air and squeeze soapy water over the top of it. If you get bubbles you have holes.