Glad to hear that you survived the festival and the ride in Dogon.
I took the ferry headed north a couple of years ago to avoid the road in rainy season. Can't remember when the worst of the rainy season is, but guessing that February is ok for the Ekok-Mamfe road? Someone on here can confirm but if it isn't the middle of rainy season, that would be my first choice.
If it is rainy season, then it's pretty easy to take the ferry south. It's mainly a passenger ferry, so you have to negotiate with the touts to load your bike. If you are lucky, there is room and it'll fit into the hold in the back, (which is sort of like loading your bike down off the dock and into the side of the Aswan ferry).
If you are unlucky, then they will heave your bike onto the prow of the boat, which as you can imagine is a terrifying experience as you watch your bike passed over a thin plank with only a few skinny arms holding it from dropping into the ocean. This process has to be reversed at the other end, much negotiating to get it off as they will start high and you have to grind them down. The ferry runs a couple of times a week, leaves in the morning from Calabar (at night from Limbe).
From what I remember, ticket is reasonable, they will try to charge you for the bike as cargo, depending on what you can negotiate. Loading and unloading is another cost to factor in. Ride safe.