Lovely work !
I'm sure that will help out many others. Very kind of you to do the write up and share here.
Just on bending the pipes, only the other day I had a similar joggle I had to do for a custom heater set up in a short length of pipe. I have done these with benders, but with the bends so close together, it's not easy to keep them 'flat' in the other plane (if that makes sense). I toyed with the idea of machining up a press tool for doing these, both at the same time in the press. The idea being, lay a cut section of pipe in a lower die, fit the upper die, press and (hopefully!) a perfect and repeatable pipe section comes out. I've not made these types of dies before, however, I have done others for folding sheet metal with great success. As the volumes are very low, I've only done these in ordinary mild steel and grease them before each use, also making sure the steel is clean before pressing. Some of these soft tool are over 10 years old and done probably over 100 pressings, still going fine. I have also had these plated, which has increased their wear resistance and also stops them rusting.