dry aging deer roast
I suggest it's not a question of how much curing salt, but how long you leave it on.
I'll also warn you about slow cooking or BBQing venison. I once did with two beautiful venison loins what I'm afraid you're considering doing. They looked perfect coming out of the pit, but they were *grey toothpaste* inside. Deer carry their fat subcutaneously, so don't expect venison to cook like beef or pork.