We can assume this is a CB750...............what year and model? How many miles? How long have you owned it and any bike history? The tapping could be a loose adjuster nut hitting the inspection cap. Or it could be out of adjustment. Or, it could be a recessed valve seat that would allow the vavle stem to hit the cover.
Your oil leak is most likely from one or more of the oil seals. Head gaskets don't leak oil unless the oil seal allows the oil to get to the gasket. I did not look at the video because of dial-up service, but the gushing type of oil leaks at the front of the head between the exhaust ports is caused by failed oil seal pads beneath the cam towers.