Just an update to this: My torque wrench is regularly sent out for calibration, so is accurate. I haven't been able to do much riding since replacing the last bolt I broke. However, I did mention this while I was at my local Trek Store for an unrelated repair. Their suggestion was to replace the bolts with OEM, and if any of them break they would warranty the crank as defective. Sounds like a good plan so I'm going that route.

Matt