In general the coil side of the overload relay contact should never leave the starter. If you take it out of the starter, then a ground fault on the control circuit could prevent the overload relay from doing its job . The overload relay's fuction is to open one side of the power circuit to the contactor coil when the "heaters" sense excessive current. This contact is closed under normal operating conditions and opens under overload conditions.
The pressure switch contacts should not connect to a contact...they should be connected to the power side of the control circuit.
We really need a complete control sequence of operation to have any idea how this should be wired. Do both compressors normally run at the same time? Are the pressure switches designed to be a start/stop circuit with the compressors starting when the pressure drops below a preset point, and stoping when the pressure rises to a higher preset point?
