I'd putty over it... there's no way you can pull all that back and have any decent strength left on the metal. Next time you crash (knock on wood or whatever ritual you prefer) things will probably get muuuuuuuuuuch worse very quickly.

If it makes you feel any better (doubt it) I have the same tank, dents and all, only in blue and glad wrapped sitting on top of my fridge... no, gf is not impressed.