I would try to find why it is those titers keep rising. I agree PEX will probably not be effective is there is an active infection (which is, as far as I know, the only reason for titers to keep rising). From what I've heard Dr. T is very thorough and will probably order tests to see where the infection is coming from and find the best way to treat it. Maybe he can even prescribe a steroid taper to get symptoms under control until you are ready for the next step.
that is precisely what we need to happen. Thanks for the pointers. I am starting, just starting, to get a basic understanding of what is happening to his body.