Beers - Is the 160 deg F inside temperature is a recommendation kind of like 8-pound triggers on a rifle?
Could well be... I know it's not necessary for dry cured meats. As to the syringe question, it shouldn't hurt, and can save you some time. Without the syringe a large muscle should sit in the cure for 2 - 3 weeks, refrigerated. I don't really know how much difference, timewise, the syringe makes... I've never used them.
You see, the bacteria are already there... you don't have to worry about pushing them in w/ the syringe. It's up to the salt and the nitrate, along with the lack of moisture, to keep them from multiplying and causing problems.
You might consider adding some other seasonings to the cure (juniper, thyme, rosemary... you get the idea) and trying it without the heat/smoke, and see what happens.
All that said, if what you're doing looks, smells and tastes good; and hasn't made anyone sick, then keep it up. If it ain't broke....