I use arm drags in a majority of my grappling takedowns. Arm drags generally require the opponents arm to be at the same level or lower than yours. Since he was taller and kept his arms high, arm drags weren't much of an option. Arms drags also generally don't lend themselves to striking situations unless you can get some kind of tie up.
Yes, but the backwards/lateral defensive mobility generally negates this, especially if the opponent is bigger.
I believe he had no grappling experience. He didn't sprawl, but he did have a pretty good instinctive defense to the low single.