The SDK just has documentation, samples and tools. The actual compiler is within the sim, so it appears your sim may be corrupted (or perhaps you have some hardware failure).
You can reinstall the sim without re-installing all the Official folder. Just rename the Official folder temporarily, uninstall the sim, rename any C:\Users\yourname\AppData\Roaming\Microsoft Flight Simulator folder temporarily, rename the Official folder back, re-install the sim (making sure the install looks in the right place for the Official). After testing to see if it works, you can then rename your C:\Users\yourname\AppData\Roaming\Microsoft Flight Simulator folder back.
If that isn't the problem, then you may have a hardware failure... memory failure or lack of memory most likely or perhaps an overclocking problem.