The 500 error is likely caused by a PHP malfunction, this code means the webpage can't be loaded properly. It could be a bad PHP configuration (the most probable scenario), a syntax or function error somewhere in the code... Without a log is impossible to know exactly.
Do you have any log file? You should check on your appropiate logs folder (I don't know how that works in Windows, my server is Linux based). Usually, the last line should tell you what gone wrong when loading the webpage and with a little bit of research you should be able to adress the issue.
Btw, I'll send you a DM by Discord. I'm interested on those files, maybe we can help each other... ;)