Yes, Brandon served a two year mission for The Church of Jesus Christ of Latter Day Saints in Chile
As Brandon Mull graduated from college in 2000, we can assume he served his mission in the mid 1990's. He has never publically released the official dates, although we do know he served in Chile.
No, he is still alive with a wife and kids
I think he is in his early 30s. Not positive.
Yes, he does have kids