You can use lots (I think it's 8) of insims on one port at the same time. Just give them all the same port and it will work
But analog gauges need d3d8.dll and drift gauge need d3d8.dll too and how can i use 2 dlls in 1 time? I think source code is different
You can't. EDIT - The d3d8.dll is nothing to do with InSim - it's a DirectX overlay. Best bet is finding someone who will combine the two into a single app - but even then not really worth the effort.