Yes on the compression test. It should answer any questions about the condition of the rings and/or head gasket. That said I wouldn't expect that uniform a look across the cylinders if blow-by is the issue. Nor if the head gasket is leaking.
It leads me to suspect something at the top end is allowing the oil into the cylinder. About the only thing I can think of is worn valve guides. Did you replace them when you put in the new valves?
Finally, check your oil level. If it is really high you might have the problem mearstrae describes.
--David
1959 TR3
1970 Series IIa 88" ("Homer")
My hovercraft is full of eels.