Mike Islander
WKR
I had a similar issue with a tough old buck. Aged in the shrink wrap in the fridge for 5-8 days did the trick; no marinade necessary. Also, cooked very slowly to 135 F. Fast cook and high internal temps turned it back into a chunk of jerky.
I had no luck with aging in vacuum bags. I put several packages of elk in a cooler in ice and kept them that way for 28 days, trying a package each week. In the end there wasn't enough difference for me to notice. On the other hand, there was no spoilage either.
Maybe try the optimum wet-age period of 21 - 42 days? Works for beef.