Losing Oil pressure

With 20w50 oil in it if it drops that low, I would consider rebuilding it.
20w50 should give a lot better pressure at idle.

I bet if you put something like 10w30, or 40 in it, the pressure would drop to nothing idling in gear, right?

That being the case the clearances are getting up there and it's time to tear her down and do a rebuild before you scratch things up.

Like this...