The answers to the questions are . . I don't know, I've not used the system yet!
Actually, I can answer a couple of questions. There is no return loop in the system, per se. Steam enters the manifold at one end, and what doesn't inject directly into the tun will be allowed to escape into the atmosphere on the output side of the manifold through a ball valve. That same valve will also determine the pressure in the system. As far as keeping the water level above the element to preclude dry firing, not too concerned with that as there should be plenty of water above the element during the course of a mash regimen that uses this contraption, and still have enough area for the steam to build in the head space. I'll be sure to run a few tests before putting it into operation though, to confirm all of that. I already have a propane/ electric hybrid system and built a pair of triac controlled voltage controllers for the 240v elements in my HLT and BK. I can dial in whatever voltage I need after heating the water to the correct output of steam not having to "chase" the voltage output with a duty cycled solid state relay arrangement.
After my initial tests, the first thing I will do is set it up to perfectly maintain the mash temp for the 60-90 minutes of the mash without losing a single degree on the thermometer. After that, I'll go to the next phase of doing a fairly basic step mash and see how it performs. Then I'll be able to report back the results.