If it was damaged significantly enough to leak gas, I wouldn't mess around and cheap out. I'd replace it. But then you have to deal with the VIN# is stamped on it as well
The paperworks not fun but a fairly straight forward swap.
I've seen inside plenty of Buell frames and I'm not aware of any sealant inside a OE tank. Perhaps from a previous half-ass failed attempt? If it's meant to be submerged in gasoline and survive, I can't think of any way to remove it within reason.
To me the "subframe" is the part that is bolted on to the frame as a unit that holds the seat and battery tray.
