May 25th, 2013, 12:50
I'm sorry to read that you are having so many problems with FSX and Win8. I know its too late, but I would not have uninstalled the program without trying a few more things.
You indicated issues with the settings on your controller. One logical step would have been to remove the FSX.cfg file and start anew, including resetting your controller. This also would have returned you to the default flight. Many engine settings are contained in the *.flt files, so by returning to the default flight you could determine if that had been the cause for the engine not starting.
I'm new to FSX and Win8, so I'm still learning a lot which is why I'm interested in your progress. The other day I came across a thread that talked about an issue with throttle settings in FSX and recommended a change to the Standard.XML file which happens to be the main file for your controllers. The issue, apparently, is that the throttle does not reach 0% or 100%. Shutoff for me closes the throttle at 4%, for example. Anyways, my point is that we did not see if this files got corrupted or modified on your install.
As for your current situation, I don't have any advice for reinstalling FSX. What kind of issues or error messages are you encountering? Are the messages related to the registry, UAC or something else that is preventing a reinstall.