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It's good that you tested before the filter. Although a clean filter is always a good idea, your test all but rules out a filter being the main problem.
The rate of leakage shouldn't be preventing the pump from making and maintaining pressure. If the pressure dropped immediately after the pump shut down I would be more concerned over the leakage rate.
Fuel pumps are extremely sensitive to voltage. You need to verify that the pump has 12.6V at the pump, not just in the pump circuit of the wiring harness. There are several connectors between the pump relay and pump itself. The most suspect connector is right at the fuel tank pickup unit. They tend to heat and fail, causing undervoltage and the resultant low pressure.
