Depending on the area and map (remember 1.5.4 isn't fully EDGE yet), I get between 30-90. Closer to the ground in populated cities is closer to 30, up in the sky dogfighting is closer to 90. But in 2.0.2 I've always gotten higher fps around 60-90. So looking forward to 2.5 when everything is fully EDGE.
The grass friction test was pretty cool. Wasn't really expecting it and being the one flying and in the Oculus rift - it was pretty scary.
As scaling, I could see it being a lot of work. But since I we haven't tried to put more then two people in, not sure how well the engine would handle it.
Yes it does. It actually doesn't care if your in single player, multiplayer, or multi crew. It just gets the info from DCS and sends it to the simshaker.