Yes, they killed a lot, it took half of the Euroasian land mass to even have 100 million. That's a lot of people.
The 5 million for Central Asia is probably about right, but keep in mind, for some reason, they really didn't like Muslims much. They were much more "civilized" around Christians and Buddhists.
After some additional research, you appear to be more or less correct. The total number is probably closer to 50M than 100M.
Still a major accomplishment, given the population they had to work with and the technology available.