Reply to "Fuel line no gas again"

The green stuff is undoubtably copper salt- a reaction compound between copper/brass and water or acids. The fuel tank drain plug is likely age-welded in place and may need drilling out. The vendors usually have replacement plugs; an air-impact gun set on 'medium impact' and patience as it chatters away on its socket for a few minutes, sometimes will loosen tight plugs without damage to either plug or tank.
Given your problems so far, I'd completely empty the tank however you can, run a shop-vac hose in thru the filler or sender hole for a few hours to dry it out, flush it with alcohol to remove the last traces of water in tank seams, then proceed as if you were restoring an old car's tank. Expect perforations in the welded fuel-out line if its a pre-'73 tank. This will eventually cause you to run out of gas when the level gets to the lowest corrosion hole in the line. Changing to a late fuel sender with integral fuel-out spigot cheaply cures an inaccessible perforated line. It is a true bolt-in mod; one of a very few.