ol' slant is dead... need help!

In order for the metal slivers to reach the little holes in the oil filter, they had to go through the pickup tube and oil pump. If the rotor and/or housing of the was scored by the metal passing through, the pump will not develop full pressure. Would it be enough to damage the engine if not replaced, I can't say. I suggest a compression test to determine if the problem is rings. You don't need to start the engine to run the test, but it will need oil.

Putting el cheapo oil and filter in it to see if it knocks is a good idea. It seems to me that the engine was close to the end of its life, at least without a rebuild, and you happened to be there when it expired.

FWIW: A carbureted engine in my experience will suffer vapor lock before internal damage occurs. As engine heat escalates, it begins to rattle or ping. At first this only happens under acceleration. Right before it vapor locks, the engine will ping when the throttle is opened even a little bit more.

When replacing coolant in an engine that has puked its coolant, let the engine cool down first. Putting cold coolant in a hot engine will at the best shoot a jet of steam back out the radiator and at worst will crack the block or cylinder head.