Well, I got the Dreamcatcher + Passive Antenna on LNA_IN working. I now have a SNR of 8...?!
It's directly attached to the SMA port (no cable). That's really good news; apart that I don't know why it was not working before?
When I'll reinstall everything, if I come to the same poor signal and I can figure out why was it happening, I'll post my findings.
Meanwhile thanks for the great work building the Outernet!