I have taken a bunch of elk and a handful of oryx and although the 6.5 CM will work it is on the very light end to take that size game consistently and cleanly. You would be best advised to use a different rifle with more power and lighter weight for those hunts.

Your choice of rifle/scope will be fine for the range and for medium size (deer, pronghorn, etc.) game as long as you will not have to walk far or shoot quickly.

I have never heard of anyone hunting mules. That will probably make some rancher very unhappy with you.