No idea on the bulkheads, sorry...Martinsreef would know more on that.
With the reeflo snapper and the number of ball valves and elbows in the manifold, I'd say the flow is fairly low. With a reeflo dart instead of the snapper, it might be enough for a softie tank without additional powerheads. But since I wanted more (random) flow, I'm also running a pair of mp10wes.
It depends on your needs, but with an appropriately sized pump on the closed loop in addition to a couple returns I think you could have plenty of flow in your system...just have to design it for that purpose. My closed loop does a great job of keeping flow in areas that would normally be dead spots even with a pair of powerheads, but the way it's currently setup wouldn't provide enough flow for my nems/sps. I do move them around every so often to create turbulence in different areas of the tank and clean off the rocks some...but most of my flow is provided my the MP10s and return.