Looking at the setup, it could well be the bung (in the top of the steerer) that you are using. That fork steerer is CF? if so, that makes the type of bung being used correct, but there are several different designs of bung, and I had one like yours which would never do up tight, replaced with a different design one (not a star-fangled nut), which fixed the issue.

For the crack, as #Yellowbeard notes, it's designed that way, the whole lot looks like it could do with a wipe over clean.