Generation IV Internal Engine - oil problem and valvetrain

So I had an oiling issue with a pinched o-ring.

Led to bearing wear- but oil pressure still good (only dropped at high rpm)

I just took the car out and it was hard to start.... It had been for a few days.
lots of up and downs in RPM for a few minutes- changed throttle body so I assume it was just the tune.

Before I took it home it was significantly harder to start (usually the problem went away once the car was warm). Car also made some noises (clacking audible from inside) while I tried to start it.

Got it home and left it on- Popped the hood and there was significant noise from the valvetrain....sewing machine, and clacking (sounding like it was coming from the intake manifold up front.

What kind of internal damage would cause a progression like this?

I would put a mechanical gauge on it and double check the oil pressure, chances are you hurt a lifter if its coming from the top of the motor. If you have a stethoscope I would run it along the bottom of the oil pan and see if have noise in bottom end.

removing the heads tomorrow- what does a collapsed lifter look like?

do I have to remove the water pump and radiator to get to the heads or is it all from the top. I already have the valve covers and intake off.