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First question is did you remove the plug that you show at the first of the video that is up under the main cap. If not you need to because there is a bottleneck under there. It needs to be drilled out.
Now on the pressure relief valve in the Chinese oil pump that is not a problem with that hole being exposed because that is just part of the valve that bleeds the oil pressure back it is not what actually stops the oil flow at low pressure. You will find when you pull that out that the valve has other orifices on it and at the head inside where the spring sets is solid.
I believe you need to pull that valve anyway to clean up the passage behind it.
I think that you're over thinking that relief valve is what I'm trying to tell you and that your new Chinese pump is just fine..
Also if you're going to use the crossover to feed the number one main you didn't need to drill out the passage coming down from the passenger side to the main. That being said if you do use the crossover you do not need to drill that passage out bigger anyway because it is only one rod being fed from that journal.