FSX is not installed on my new computer, only FSX Steam. As I mentioned before, FSX would not install on my new computer.
If you are sure the original FSX was *never* installed at any time, not even in a previous Windows installation you might have upgraded from, then FSX:Steam should be installed correctly.
However, fact both GSX and the QW757 are not working, seems to indicate a problem, possibly related to system libraries or Simconnect.
Maybe one of the add-ons you installed is using a very old Simconnect version ( there a 3 different versions in FSX ) and because of this, FSX is "stuck" with that version, which is preventing other add-ons like GSX or the QW757, which instead use a newer version, to work. This was reported to be happening, and it was a consequence of the very tricky Windows "Side-by-side" .DLL loading method, which in theory ( when it works ), should allow multiple programs requiring different versions of the same .DLL to run at the same time, but when it doesn't work, it's a nightmare trying to fix it.
The Level-D module running, with no aircraft available, also seems to indicate some problem.
Fact is, you are using a product that came out in 2006, updated in 2007, and marginally fixed in 2014 with the Steam version, I really strongly suggest, if you have a new computer, to check MSFS 2020 instead.