Wonder why low fluid was causing it to stall, wierd?... Glad you figured it out. I always hated doing tranny fluid changes, I never know how much to fill and when it's done taking fluid. I start it, put in gear, then check the level. AFter about 4-5 cycles the level stays reading full. Then after driving and getting it hot three more things can happen....
1- fluid gets hot and expands and causes the level to read even higher.
2- various clutch packs will pressurize and purge out air pockets, and causes the fluid level to read lower.
3- air pockets cause the fluid to foam up, which causes erratic shifting, and also makes the fluid level hard to read.
It's a pain in the ass, but worth it in the long run.