The crack in the exhaust port wouldn't affect the compression. But it looks like you do have issues with leaking coolant. Am I seeing rust in the combustion chambers? Could be just a bad head gasket and the coolant caused rust on the valve seats giving you the bad compression results. Or the crack could be a symptom of the head warping. I would not try repairing cast iron cracks in heads unless they were something special. My non expert opinion.