Plex Server will not start after complete reinstallation | log makes it look like a file wasn't created looking at WAP

Not a good idea. This will only place the program code onto F:
However, the Plex data folder is still on C: – and that is the one which is growing all the time.

Your new installation is still using the default location on C: for the data.
It is also likely, that the main Plex database file on C: is damaged, due to it running into a space constraint.

The way forward for you: