Steve, Concerning the vent issue, I can only share what I did.
I sealed the lower vent and left the roof vent open. My theory, at least, is that way the refrigerator will draw it's air from the lower, front of the unit flow rearward, over the coil and then upward out the roof vent.
That way the unit is getting room temp air,(not too hot or cold) and working the way is designed to work in a home.
Again, right or wrong? I can only say my refrigerator has been in two years now, working full time and doing fine.
Good luck with your project.