Give the tank top a good cleaning and double check. This is something you need to SURE of, not "sort of". FYI, there is a greater chance of holes being under the wood than a lesser chance. The reason is because aluminum does a good job of self protecting itself... but it needs good air flow to do so. I'm not saying there ARE holes there, just mentioning that to redirect your thinking on that.
Gasket... but how does the mating surface look?
I can't really tell, but what's going on with the vent hose? It looks odd.
Yes, pressure test.
I don't recall if you mentioned what engine you have, but if you have a firect fuel injected engine, it's not a good idea to use fogging oil as it can foul the injectors and/or any sensors that may be in the air intake.