The 70 psi static reading isn't meaningless.... it tells me the ambient temp when you took the reading was somewhere around 70F.

The safety cut-out switch doesn't activate until the system pressure gets very low, like around 20 psi. Since you can jumper it and get it to engage it would appear at least your 1st issue is in the compressor control circuit or a bad safety switch.

Another can of R134 won't help - 70 PSI is plenty high enough to energize the safety cut-out circuit.

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