You are correct about the no-spring brakes. In fact, the car has to be running and in low or reverse for the valve to move back out.
It should have come up on the converter when you released the button, regardless of whether or not the brake released. I think you said it came up to 5000+ with no chip in the 2-step. As depressing as it sounds, I still think you have an electrical problem instead of a tranny problem. Have you traced the tranny brake wire all the way to it's power source? Since the car had a delay box in it at one time, there may be something else in the circuit......you should have power coming to the button, and wire from button to trans. The 2-step should be spliced into the wire going to the trans. That's it, nothing else should be hooked to it......