lost all oil pressure but not flow

change the 5w30 to 20w50 and see where you're at.

My last 440 I used full grooved mains and had barely 10psi per 1,000RPm. Ended up running 20/50 in it and it was fine.

My current 440 uses 0w40 and still has oil pressure on the high side but I'm not complaining.

Both engines have been together for almost 20 years so..