After two years of sourcing parts and getting some welds on the tank, I like to report the first test having been successful. Although I do not have access to specific foaming agents, the test with regular dish soap created foam - and that's what I was hoping for. There were no issues, but a few leaks at the hose connections due to the hose clamps being of inferior quality and needing replacement. After that, it just worked fine. Now would be the time to secure real foaming agents that provide dense foam to be mixed with cement to get "Foamed Cement".
For anybody interested, I would write up what parts were used to create this foam generator.
It means a lot to me that I was finally able to finish it, after a plethora of obstacles. And I may never be able to really use it, as I am confronted with insurmountable problems now. I hope You like it.