Sorry to hear you’re having so much trouble. I wouldn’t suggest anything new at this point, except you did say you were likely to throw it all out. If you really do get to that point, I suggest:
https://community.smartthings.com/t/smart-sprinkler-system/3076
It cost me about $60 in parts and has been a champ. It does not use rain sensors, but NWS input on rain, actual and forecast.