The one on the trigger level side should be steady. The other one, I think, should also be steady if the coupling is set to TV-V/DC, but let me review the schematic. Are you saying they both settle down to 0 volts no matter where you put them?
Yes, we are getting to the point where another scope would be extremely useful. I don't want you to damage your computer, but I suppose as long as you used high value resistors for the input maybe it works. Do you have soundcard scope software and an adapter cable? Your sig-gen might be useful too, but the output is low.