I know exactly what you mean. My little one will do things for others that he will not do for his parents and he has been that way since he started receiving EI services at 7 months old. When I was starting respite and needed to add a respite goal, our family service coordinator was very adamant that the goal needed to be about me so we come up with "Mom would like to receive support engaging her child so she can complete other projects and activities." Our progress marker was "Mom will report at 6 months that her stress has decreased." Of course this was for EI and I know things differ from and IFSP to an IEP. Can you say that you would like to "receive additional support engaging your child so he can continue to make steady gains in his ability to create relationships outside of the family" or something like that? Respite is about the needs of parents and as hard as it can be for us, it is OK to say "working with my kid is hard and I need a break!" Being a parent is a different role than that of a therapist. Yes, we work on goals with our kids, but it's not the same and it can't be the same or it drains your relationship. You need and deserve time to step back and regroup - thus the availability of respite care!
I know where you are coming from and am crossing my fingers that you get your additional hours soon AND maybe a new service coordinator who is respectful, understanding, and helpful.