Thanks for the writeup. I am not at all impressed with BMW's concept of maintenance on the E90 (minimal maintenance). This is setting these cars up to fall apart prior to 200K mi. Personally, I like to drive a car until the wheels fall off.
6) Place the used oil in the container to see how many quarts came out of your transmission. 4 1/4 quarts came out of mine. I know, I know, what about the torque converter. Something is better than nothing. Plus I plan on doing this every 20,000 miles so the next change or so should get alot of it out. (Castrol recommends 15,000 to 30,000 miles changes). Besides, its lifetime fluid so who cares about the fluid in the torque converter.
My wife's got an Acura TL. The same thing there; you can drain ~3 quarts out of ~9 quarts. The solution among many of the Acura DIYers is to drain 3 quarts on every other oil change once you hit 30-40K miles. That's how I've been doing it for her Acura and will likely do the same with my BMW.