Surely the simple answer is don't let the tank get that low before refuelling? I never let the fuel level on my Micra go below 1/4 full, then brim it again....
Surely one of these 6mm spade terminals that can be bought in any motor factors, attached to the area that the original broke off of, with conductive cement...
Why replace steel Rivnuts with aluminium ones in a steel panel, taking steel screws in an obviously wet area Paul?? You are just asking for galvanic corrosion to occur, far worst than the original surface rust, on the steel Rivnuts....
Any real performance gains are made by increasing the size of the air collector and the input pipe. The difference in cross-sectional area of the 60mm inlet pipe is almost 80% greater than the original pipe and as such gets a lot more air into the filter box....