Without knowing this stick, I suppose I'd check:
1. Kernel support (the stick sounds old, so 3.10 might be fine or you may need additional drivers)
2. See if those kernel modules are actually loading and are the right ones
3. Any firmware required?
4. Access permissions - can the tvheadend process access the video devices in /dev/dvb or similar
5. Anything in syslog from tvh beyond what you posted
6. Anything in dmesg beyond what you posted
7. What precisely does the tvh web interface tell you - can it see the tuner at all, is it enabled, etc.