Worse case scenario a new shaft is under $200 or so at TSC. Penetrating oil, some heavy pulling while chained to a tree & maybe some heat might work. Cant hurt to try. Dont hitch it to the PTO on your tractor to try & pull it apart. Liable to break expensive things that way. Chain it to the hitch.
My old PHD ran fine for a long time after I bent & mostly unbent the PTO shaft... Twice. I was slightly off on reengineering the PHD to fit on my QH. Worked great as long as you extended the hydraulic toplink before lowering the 3pt.