When my charge pump died it just wouldn't suck oil when I first started it. If I parked with the front facing downhill it would get enough oil in it. But it was like a light switch, either it would get oil or it would not and it was always starting. I think at this point in time you may want to get a manual (maybe off ebay).
I think you need to find the pressure valve in the transmission and see if the gauge is reading pressure before or after it. My guess is after it, that's why you either have good pressure or nothing. It could be that valve is faulty and is shutting off fluid to your torque converter. How quick does it happen? I would think a bad torque converter would show up more as a slipping feeling, something that would either start off slipping and just continually get worse as the oil heats up and thins out.