Thanks for waiting, guys!
While Jason is vastly inferior in durability, one shot he is not. The nature of Jason's abilities means that if the tank is destroyed, his Repair Kit pretty much insta-heals it back to full. (He has 14 of those, plus the same number of Armour Kits and Health kits) Besides, in character, he's unlikely to be using the tank, more the Bustard, which has more powerful weapons.
Also, Jason's most powerful weapon, the Los Alamos Nuclear Launcher, can do this:
https://youtu.be/oZkFQXYag1Y?t=32. Not sure how powerful that is, but I would hazard a guess that it's a fair bit above 4 tons.
In terms of abilities, there's a couple that Bambu left out of his (extremely comprehensive) analysis. Namely, Jason's Poison/Disease manipulation, which can neg the impressive durability that the Beheaded throws around. And finally, since I know I am forgetting the Beheaded's resurrection/Regenerationn, Jason has faced supernatural foes before, that have straight-up refused to die. What does he do then?
BFR's them right to hell:
https://youtu.be/EYXF11mMyvk?t=627
And since the man's favourite tactic is spamming high-explosive artefacts in his foe's general direction, getting the Beheaded weak enough that he can stride up and hand him over to the Devil shouldn't be too difficult.
There's a wall of text on the Beheaded's profile that can make life for my little GTA ripoff pretty hard, but he is far from helpless