Please consider turning on send info to Mozilla before posting a question. This helps us help you. As I have no info from your system that would help see things that cause issues. EXCEPTION_ACCESS_VIOLATION_WRITE is the crash reason. I believe associated to Graphics Card, Flash but no one reason.

So please updating your video card drivers it is a must and the first thing to start with : https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration TRY WITH NO ACCELERATION ALSO

Ok so you have been uninstalling and stuff so lets do that again after you have updated your video card drivers.

Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved.

Reinstall Firefox 56.0.2 with a Full Version Installer https://www.mozilla.org/firefox/all/

Did you use the small stub installer before. If so this one may possibly work out.

If/when get Firefox up do this right after please : https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems?redirectlocale=en-US&redirectslug=Troubleshooting+extensions+and+themes

Please let us know if this solved your issue or if need further assistance.

The is a bug report related to the crash "signature" which seems related to hardware acceleration, so graphics would appear to be the developers' best guess as well.

If I understand the crash report a bit then it looks that there is a problem with the compositor thread that makes Firefox shutdown the compositor that runs on Windows in its own processor thread to be able to restart the compositor to recover from errors. The crash seems to happen because Firefox doesn't seem to know that the compositor is being shutdown and tries to access this old compositor process.