hi porto ,
many have experienced the same
if you can find a fabricator , that will work by welding a fuel tank , many wont look at it hands down , but there are some out there
usually a plate welded to cover the hole will work fine , BUT , be aware that up the side of the tank in the same area is another likely weak point , where oxidisation has thinned out the aluminium skin , as you have seen near the fuel pump . its a low point in the tank where water will sit and oxidise away un-noticed for years
whilst its apart ...probe in that area and get it done at the same time
good luck