I can help you with your framerate.
1)Go to your Preferences folder in output, and delete/replace everything in that folder to another folder on your desktop. You do have to re configure your controls, but it should increase your FPS.
2)Download the newest FlyWithLua plugin, put that into your plugins folder. Then download the Auto_LOD plugin and put that into your FlyWithLua scripts folder. This should also help with your FPS.
I've done both of these things and my FPS has increased with 20/30 fps...
Also, maybe the problem with the XP crashes is that your Main X-Plane 11 folder is in some other folders called like: Games, or Flightsim. Laminar suggest that you don't do that, so if you have done that, place your X-Plane 11 folder on your Desktop. I've done that too 1 week ago, and haven't had any crashes.
I hope some of this has helped you!