I think you need to brush up on your basic understanding of hydraulics. It would seem you don't have a complete path right now. So essentially your pump is deadheaded causing your relief valve to lift. This will in short order overheat the oil and cause a lot of damage.
Your tractor has on open center system which means there is a constant flow of oil running through it. That path must be maintained, the oil has to go somehwere. Your picture shows no jumper hose. No oil flow....
The reason your stuff worked with the driver installed is it completed the path and oil flowed on to the rockshaft.
Make a jumper hose from P, pressure, to PB, Power Beyond. Return doesn't get anything in this case.