Please, find attached a new couatl.log file (it reports KIAH is not installed? 
It reports that, because it can't find the KIAH .MDL files that is supposed to patch ( to allow for some differences in rendering between P3D and FSX ), that are also located under C:\ProgramData\Virtuali\FSDT_KIAH
Since you removed the whole C:\ProgramData\Virtuali\ folder, you will have to reinstall KIAH as well.
But this is not really the issue, the issue is that the program still can't access the C:\ProgramData\Virtuali folder, which has been created by its own installer.
The only possible explanation left, is that you have another software, probably not even related to flight sim, that is locking access to that folder for some reason. Sorry for not being more specific, but if another software has gained access to that folder (maybe the whole C:\ProgramData, perhaps an antivirus or similar product is doing this), there's nothing we can do it from our side, if the folder is being locked out. The only possible solution, is finding the offending program.