It is hard to juggle routines with all the other commitments. I don't think what you are currently doing is wrong, I personlly do not train back with anything other than a small bodypart (calves or maybe hams at a push because you can do stiff legged deadlifts for lower back and hams) because back is such a large complex muscle group.

Doing back and chest before bi's and tri's can be a good pre-exhausting method and it has been a while since I trained arms solely on their own (I think I will just for fun this week )

Paul.