I never bothered with a small torque wrench until I bought an Enfield. The bolts on that bike are made from some kind of engineering paneer and kind of make the proper tool worthwhile. I bought a nice quality 1/4" drive  click type torque wrench  from a bicycle tool supplier. So far, so good. A deflection beam type would be better but they're not cheap.
Too bad about the broken bolts, hope you solve it without too much pain.