The jammer you have is actually a centre main jammer, the sheave does not do much for the Genoa sheet. Maybe you should get rid of the device and put a cleat only on a pedestal positioned against the inside edge of the benches, across from the turning block on the gunwale?
Here is my solution
The sheet comes from the Genoa, through the block on the track. Then to a ratchet cheek block on a slightly angled pedestal between the benches and from there across over the bench to a swivelling cleat. The swivelling cleat with a simple fairlead is nice for single handing but not really needed. Alternatively the cleat can be put on a wooden pedestal in the direction of pull. In your case perhaps between the bench planks? Also the cheek block can be replaced by a floating block on the gunwale like yours, or even a floating ratchet block. I made the pedestal from plywood, painted with two coats of two pot paint so it blends in with the rest of the boat. The positioning of the blocks and cleats is not important. As long as you leave the rail and the block on the rail in the same position the sailing characteristics won’t change.