Only thing I could add to this is that most if not all jerky recipes call for meat sliced to 1/4" thick. Now I know you are asking, " What about all those packaged bags of jerky at the gas station?" I just don't think that stuff is real.
But think about it. If you base your recipe on 1/4" slices of meat and call for a certain period of time, then it would have to be quicker for thinner and longer for thicker. I think you over cooked it. Personnaly, I taste test mine often and pull it out when I like the texture. It is already seasoned and cured so all your doing is making it like you like it.
The fight ain't over until the winner says it is.
Backwoods Party, Bubba Keg, Primo XL Oval, Ole Grandad, Mini BGE, Bradly Original Smoker, and a Weber kettle.