Although I've never had this particular difficulty, I have just accomplished yet another FSX/Accel/SP2 uninstall/repair/reinstall due to me not being nearly as knowledgeable about fiddling with add-ons as I thought I was.
Texture and effects files/folders sure are touchy things. They don't like undereducated types like me sometimes.

If I had a dollar for every fatal error due to an fsx.cfg difficulty, or somethin' similar, I'd have enough for a new truck down payment!

Some I could fix cause I'd had an entire (original) FSX/Accel/SP2 backup on a 1TB external harddrive, some I had to fix by uninstalling/deleting every single FSX related file and reinstalling from scratch.
That's what I'm suggesting for you to do. Seek out EVERY single FSX related anything in your system and delete it! Wipe it off the face of your 'puter! Look in every nook and cranny!!! Delete (after making copies on a flash/thumb/external drive) every single FSX related add-on you've ever downloaded also. Don't worry about any payware stuff, most vendors have excellent customer service that will assist with reinstalls/recoveries.....I'm on a first-name basis with a nice lady at Abacus!

I was surprised a few months back to discover that my repair techniques were getting thwarted by a hidden add-on .dll file! Took me about two weeks to discover what was effin with me.
Then do a reinstall like you never had it to begin with. Complete with reregistering! Some say they have had problems with doing a reregister with MS, but I have actually done it, on the same PC and IP address, nine times with zero difficulty.
It would seem to me that something somewhere is derailing your repair effort(s), so it would seem that you need to do what has worked for me in the past........actually very recent past........please excuse me while I go and reinstall FSWC.
It's the last thing I have to do to get my latest FSX malady cured.
Hope this helps! Sounds drastic I know, but it seems like you're in the same rut I've climbed out of more than a few times.
Best o' luck to ya!!!!