My question is, if we were a PTA instead, is there some other chain of command that could be addressed to help resolve these issues?
I would say that the answer to that is a definite "maybe." In theory, there is at least a state unit above your local unit, and there is most likely some sort of regional council between your local unit and the state. Somewhere in there, there should be people who can intervene. But, it all depends on the quality of the people in those positions. I'm always very impressed by MichelleB and the stuff her PTA does; if I were in her state, I'd call her in a minute to help with something like what you are experiencing. My own experience in my state is drastically different--I would hire a mediator before I would ever let a state PTA person try to help me out.
I haven't read all your other posts about the problems you are experiencing, but I don't think switching to PTA is going to help much. If you switch from PTO to PTA, and have the same people involved, you'll still have the same problems.
From what I can recall, it seems more like what you need is some changes in your bylaws, or maybe someone to act as a parliamentarian to make sure you follow Robert's Rules.