Has anyone done an initial diagnosis on the transmission?

A couple of points:
1. There is no such thing as "lifetime" fluid.
2. Even BMW fluid is not $50 a liter.
3. There are options besides a dealer or parts house. Have you considered an ATRA member transmission shop with good reviews on Google/Yelp?
4. Gear ratio error codes could be signify low fluid, but could also (and probably are, at 166 k miles) a sign of internal wear.
5. While these cars are very sensitive to low voltages, if the charging system is good, I'd doubt that you fried anything from that alone.