I can't do the excluding the files as avast only allows folders done and I am defeinatly not doing the whole FSX folder
Why ? That's the best possible option, because it will prevent the antivirus to slow down FSX. If you don't do that, it will scan *every* executable in the FSX folder at every FSX startup.
When I install FSX on a new system, the FIRST thing I do, is to exclude its whole folder from real time scanning.
If you can give me the directory to what to delete based of \steamapps\common\ then I will know what to delete and can do it via the Linux boot drive
There's nothing to remove in the steamapps\common. Solution #3 in the linked thread told you what you had to remove.
In case of FSX Steam, I would probably try to delete ALL folders named "simconnect" in the
WinSxS folder and then use the "Verify integrity of Game cache" to restore the Steam version of the libraries AND install the FSX SP2-compatible version as explained in solution #5