Well, I didn't give up and finally got it all worked out. I don't recommend this to anybody but in case someone is hell bent as I was to make this work I will provide some info. With this configuration I think I did get some modest improvements over stock: The fan speed is infinitely adjustable instead of just 3 positions. I don't know why anyone needs this, but its an outcome of using the PWM controller. 2. I wired with a push/pull potentiometer as suggested and can just flick it in/out to turn on/off the ac control and the blower and have it turn back on the ac and resume to whatever air speed I last had it to when pulled out. I see this as a minor convenience improvement. Lastly, I now have all my wiring and "resistors" inside the car where I can access without any disassembly of the front end/clam. Hopefully I won't ever need to touch this again.
The DC controller that worked for me and passed full voltage was this one: 12V 24V 48V 2000W MAX 10-50V 40A DC Motor Speed Control PWM HHO RC Controller
It was cheap, 7 bucks plus shipping, but worked as expected passing all the power at full turn. The issue with this is it has a built in potentiometer, so I had to a little surgery on it. I cut the potentiometer off with a wheel half way leaving just the base attached to the board. This avoided having to remove the existing solder points which is a pain on these and it left me some soldering points on the 'legs' to utilize. You can see in the pictures how I did it. Because it's so hard to work under the dash, I soldered the wires and quick disconnects at both ends so the hvac controls are still removable.
I used the same push/pull pot I used for the Tony Wa bypass. It needs minor alteration on the shaft to get the right size D to fit the original knob, but as you can see from the pics, everything looks very stock at first glance. The Pot I used is available from smc: SMC ELECTRONICS - Potentiometers
You can ignore the red wire to the back of the controller. That was for the ac button power to turn on with the blower but apparently I don't understand DC electronics too well yet and that didn't work. Instead I wired the ac/recirc power direct from the push/pull power on the pot so it turns on/off with the switch.
Overall, its working great. Putting out a lot more air than before, probably because my wires were corroded.