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That chart applies to standard engines used as commuters. You can find it on numerous car driver manual.
The oil pump may have its regulator damaged, it just is a ball and a spring. Maybe you could preload the spring a bit more. The pump seal may be leaking too. It could be a lot of things ... when i changed my oil pump, it looked good too. I hesitated to buy a new one, but then i thought i had oil pressure and temperature problems, and i did not want to pull the engine again, and i changed it. That really was the source of my problems, i had to run 10w60 to have a good pressure when hot. The problem is that when using a pressure regulating system, the more pressure you get, the less flow you have.
Now i am running 10w50, and am near the maximum pressure window when hot. I also have no temperature problems anymore ( new pump gave more flow and more pressure). I probably can try going 5w50.
Now, 70psi when cold indicates the pumps does a good job when oil is thick. Mine did not, so it may be just a sealing problem, or a thin oil problem. I don't live in the same place so it has to do with usual driving temperatures, but here nissan (and most car builders) recommend 10w40 as standard thickness, and it is nowhere near 30°C.
But again, this is for a normal use of the engine. The real recommended thickness is whatever fits the pressure window given in the FSM.
Try just with a thicker oil, see if the problem goes away. Acheap 10w40 will do for a bit of testing. It might be all you need (although i am a bit skeptical)
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