You certainly have your problems. The tank seems to be the root of them all. I don't know of any thorough method to clean the inside of it without removing it from the car. But I will tell you this.... DO NOT USE ANY VACUUM CLEANER, WET OR DRY TYPE, TO SUCK OUT WHATEVER IS IN THERE.!!!!!!!
Odds of the gasoline vapors igniting and exploding as they pass through the vac are better than excellent.
