i think this is much better for the A-1 drawing....but for B-1, i would make the refugium space much bigger than the skimmer.....JMO
don't rely on a check valve. a little bit of algae, slime, snail shell, sponge...whatever will stop it from sealing.
the best way i know is to drill a small hole in the return just below the water line inside the tank. most of the flow will still come out the end and you'll be able to direct it wherever, and it will suck air almost immediately.