push button 904 seems like its slipping badly.

Definitely more than 4 qts. Check the manual, but I recall more like 8 qts if you drained the torque converter. Unlikely you did any damage. When low, the torque converter isn't full so doesn't transmit any torque thru, thus no load on the plates. My 65 C-body is like that with "morning sickness", i.e. the fluid slowly drains out of the torque converter. I found if I put it in "N", it refills in 5 secs, whereas in "R" it takes 30 sec before I can move.