For heat and smoke transfer from the heat chamber to the smoke chamber you should be able to rely on the chimney or stack effect. You should have an inlet into the heat/smoke chamber, an opening between the two chambers and an outlet at the top of the upper chamber. The inlet and outlet can be about the same size in area, and you can easily damper both for adjustability. The transfer opening between the two chambers should be at least as large as the inlet opening so that it is non-restrictive for flow from hot to cold.
For forced convection within the meat chamber, a capacity of 10X the volume of the closed chamber should be plenty - you're not looking for a hurricane, just a steady, gentle stirring of the air. In it's simplest form, just a circulating fan inside, will probably require that the motor be outside. A more complex but probably more efficient design would be augment what would be natural convection by taking hot air from the top of the chamber, running through an external duct, then injecting it back into the bottom of the chamber. A "squirrel cage" fan similar to pikeman's RR-switch cabinet would work great, but again don't overdo the flow capacity. If I did the calc right you have ~ 5.8 cu ft of volume, so something on the order of 40-60 cfm should be plenty.
Just a thought ... one design for the heat & smoke transfer that you might want to consider would be something similar to that used in the larger smokehouse from SausageMaker -- this one
. It is similar but larger to yours in that it has separate heating and smoking chambers. In horizontal wall between the two there is a central hole that in the meat chamber becomes a stack with a deflector shield over the opening. I don't think you need to extend the cap as high as they show, but the stack and cap allows the floor of the meat chamber to function as a grease catch.