If you are breaking wheel studs, you're either overtightening the wheel nuts or you have some type of wheel/tire package which is way overloading the studs and the hub.
I'd fix those issues first before I'd go looking for wheel stud specs.
In fact, if you have one of the two problems listed above and you've broken two studs already, I'd replace all 20 of them.
The torque specs for wheel nuts are in the FSM but, typically, I use 80-100 ft.lbs and I use an accurate, dial-indicating torque wrench for that purpose.
Lastly, many "click" type torque wrenches can be inaccurate. If that's what you use and you have not had it checked in a couple of years, that could be your problem, especially if it's a low-cost or foreign-made tool.