Uhh... the torque converter isn't splined to the crank but it is bolted to the crank through the flexplate! You probably didn't do any damage but don't turn the engine backwards again. To remove doubt while working on your back with your head towards the differential, set a ratchet with 27mm socket on the crank so you can only turn the engine one direction. edit - Make sure it's the right direction If you're as much a monkey as I am, you'll move the ratchet with your legs while you watch for the drain plug to align with the access hole.

I've never had a problem filling 4 quarts with the front on ramps (116, 126, 140, 124) but maybe I'm just lucky. Make sure the pan mating surface is true/flat/level before installing and don't overtighten. I don't know the torque spec but it's not much more than you could tighten with a screwdriver.

Sixto
87 300D
... working on opposable big toes