Fun stuff. Hopefully it goes a bit easier for you than my Spear has been. I spent three weeks fighting a fuel system issue where one engine would run like clockwork while the other barely ran at all. Had to spend a fair bit with the FPV system as well...I ordered a pair of Eeachine 1000tvl cameras and a pair of Eachine TX805 transmitters, cameras work a treat, but the transmitter I tried to use didn't seem to broadcast. Ended up stealing the transmitter from my CA-10 to get FPV working in the Spear.
I'm running Betaflight on a Matek F411 FC for driving the FPV OSD, but my actual flight controls are on a totally separate system. I fly on a Futaba 6J and it has elevon mixing built in so I'm running the flight controls solely off that.
Perhaps FPV is something you could do on your canard plane, too? You've already got an FC, so OSD is there and waiting.