I personally think that he is using wrestling/Hollywood as leverage, as he should. Despite his injury history, he is the best TE in the game. He should be paid like one (same for Brady, but that's an entirely different story). I know that Gronk's family has been involved in the reporting of injuries. If I were his dad, I would tell him to milk every last dime out of the Patriots, or walk. The hits that he takes are likely to negatively affect his life after football.
If you were Gronk, would you come back as is, or would you threaten to head to Hollywood until paid a salary commensurate with his talent?
I personally would try to get as much $, and I'd still consider walking, regardless of money. It cannot be fun to consistently put yourself out as a defenseless target for some safety/linebacker to potentially injure you.