I this all comes from the fact that you've never installed it (i.e. created a .deb file or similar). I would guess that user 'daemon' doesn't have write permission to /home/cubox/.hts/tvheadend, or is trying to create config files elsewhere where they're failing - perhaps /home/daemon, or perhaps daemon doesn't have a home directory at all. A lack of installation explains the lack of /etc/default/tvheadend - apologies, I should have realised that beforehand. You can switch debugging on in the web interface by opening the message pane (double chevron in the bottom right) and then clicking the gear symbol that appears.
You're starting it as a daemon (-f) which defaults to daemon/video, but the -C option is switching off access control, which would have shown up a config problem earlier, I suspect (since you wouldn't have been able to log in to the web UI and wouldn't have been able to create the access control rules properly).
Personally, I'd be inclined to use autobuild to create a deb package and then install that through dpkg. This will install tvheadend just as if it had come from a PPA, including all the config files, startup files, etc.
If that's not an option, do some digging into the command-line options (I think there's one to specify where the config resides, for example; -c <config_directory>, I think); check the permissions on the .hts/tvheadend directory (must be writeable by daemon). Also, do a find / -name tvheadend to see if there's something elsewhere that we've missed.
Apologies, short on time to help more at the moment.