First of all, the gas pouring out everywhere is almost certainly a stuck open needle/seat.

Causes:

Float is either stuck to the bad gas in the bottom
Float has a pin hole and has sunk
Float is not properly adjusted
Needle seat have something between them allowing fuel in when closed
Needle and seat are bad allowing fuel in when closed

Bad gas from sitting can cause several of the above symptoms, I'd suggest removing the fuel tank, having it boiled and sealed out or replace it. Clean out the fuel lines, fuel pump, and change the filter. It's a PIA but the only way to know you've fixed the issue completely.