This quote alone suggests you may be overstating the difficulty of getting a working JACK system up and running with the latencies you require. If JACK were as bad as you maintain, surely more people would be using the alternative? I'd thoroughly recommend you spend the time you will spend trying to get the portaudio backend running the way you want and use that time instead to learn how to set up and use JACK on your platform. In my experience, once JACK is set up and running, it is as hassle free as any other direct interface, but with the added bonus of future flexibility if required...