When shore power was available, I have used USB fans in those small areas where there is no ventilation just to keep the air moving. I also propped up the mattress and the storage cover to leave that space open to the bedroom. One other thing is that at the front of the mattress, I laid a 2x4 on the floor between it and the front wall to maintain an air space down there.
I only had camping gear in the front outside storage, so I did not have a problem there. Maybe a vent on the ceiling (it's the floor under the bed) and a vent on either side of the bed platform might help, but if you store anything that smells, it might be an issue.
Good luck!