I am going to offer a contrary opinion on your idle oil pressure. I don't expect very many to agree with me and I'm okay with that. I am comfortable with my opinion on this one.
Your idle oil pressure is fine. In that regard, it doesn't matter what weight oil you're using or what your idle speed is. Idle speed can often make a significant difference in idle oil pressure. You mid and upper rpm oil pressure is also fine.
The reason I think your idle pressure is okay? Well, you generally don't see a specification for idle oil pressure. Not by manufacturers or anyone else. Oil pressure references are usually specified as oil pressure @ 2,000 rpm or there abouts. One of the reasons you don't usually see a spec for idle oil pressure is that the engine is under very low load. It's making just enough power to keep itself turning over. Because of the very low cylinder pressure, there's very little load on the bearings. As long as the engine is moving oil over the bearings, you're fine.
The other reason is all engines are subject to stacking tolerances. These things are not being built to aerospace specifications so bearing clearances may not be completely uniform throughout the engine...particularly in the camshaft where most oil pressure is lost. It's good enough to get the job done.
Some old timers may recall this, but it was pretty common for the oil light to flicker when you were sitting at a stop light at idle. The pressure sensor would turn on the light around 5psi. This was with brand new cars. Ford's solution to customer concerns about low oil pressure? They raised the idle by 50 rpm and that turned out the light.
If you were concerned about idle oil pressure you could try running a slightly higher idle or, depending upon what you're now using, running a heavier oil. But I don't think you need to.