If you picked it up with no oil, I would dare say they had run it for a while low on oil. Chances are is the rod has snapped, but its also possible that maybe a valve has jammed (unlikely)
To get a victa blade boss off I generally find I need a fair bit of heat applied and rest the boss against something, put a bolt of the same thread into the crank, and tap the bolt with the weight of the engine hanging off the boss.
