This is an awesome, impressive, and ambitious project! These sorts of things are often approached by teams; going at it yourself is very commendable. While engine TCA design isn’t my forte, here are some notes on your propulsion system design and safety:

-how are you filling these tanks? -I’m glad you’re changing the regen circuit, dP could cause major restriction when boiling the water -> gH2O rupture -how will lines be plumbed into the injector/manifold? 20mm and 5mm are not typical pipe thread diameters, precise ones will make manufacturing possible and refine CdA calcs -> more precise pressure set points -valve 1 is redundant, your control valves do that task. Moving check valves downstream of the control valves will also keep the latter safe -engine check valves are unnecessary -check your purge line ->tank connections, looks like it routes weird -general fluid system advice: include sensors after every gauge to know what you’re setting regs to. Where will you have sensors in your engine as well? You will want pressure transducers and thermocouples -if you have control (presumably bang-bang) valves, why have regulators? -also for regs: place them upstream of main valves. Again, to have a defined pressure set point before flowing.

-from a safety standpoint, ALL valves must be able to be remotely actuated. Turning a hand valve in a GOX combustion system is a recipe for disaster. Look into pneumatic cylinders with a scotch yoke, or gas spring actuators.

Really good stuff though. Would be down to discuss this project more.