The code fixes are internal. All your tweaking isn't going to change much. Go back to SE and put up with those issues or stick with FSX and put up with a different set of issues.
I would go to Device Manager in Windows and under Display adapters, see what is active. The latest update did not change the hardware requirements for MSFS.
I'm sure you can, but there are only 3 official retailers of MSFS: the MS Store, Steam and Aerosoft. Purchase anywhere else and you are at risk for things like a one time use license.
Ok, there is only one place that sells the legitimate disk version and it's not eBay. Hope the second time you purchased from MS, Steam, or Aerosoft. Then you will never have to purchase again, even for multiple computers.
1. Saving a flight does not save every single detail of the flight. It's always been this way and has nothing to do with your OS.
2. Anything you don't want or need in MSFS can be removed. Therefore it's no more "bloatware" then your FSX install was.