LOL, that'd make me feel really silly...
Yep, I bench bled the MC. Twice, actually because I didn't check the piston movement after the first time and I thought there may be some air in the system still. I bled all four corners probably a dozen times last night and I'm not getting any change. Every now and then I'll get a tiny bubble but I'm not thinking that's air getting in through the bleeder fitting. If I was slowly getting air out of the system I'd expect the pedal feel would change but I'm not getting anything, The thing that has me stuck is why I can't build up stiffness in the pedal. If it were air, pumping the pedal would briefly build pressure and with the car off the pedal should get stiff due to the lack of vacuum in the booster. I thought the latter was due to the lack of a check valve but even when I installed that nothing changed. That's when I found out the check valve isn't holding vacuum either. I'm going to buy a cheap plastic one at Autozone after work today to see if that fixes anything.