For some reason, the last two you tube videos you posted aren't playing on my computer. If looks like you're dealing with more than one problem. I'd suggest dropping the transmission and clutch, and possibly the flywheel to eliminate the possibility of something wedged between the flywheel and the engine block. At least remove the sheet metal cover under the bellhousing and look for debris in the flywheel/block area with a bright light. DO NOT keep trying to run the engine- - - -you'll only be doing more damage. Once the rubbing noise is dealt with, then it will be time to manage the rocker arm oiling. A dry or damaged main bearing can also cause a squeal, but that's engine overhaul territory.
Pulling the side cover isn't likely to show you much about rocker arm oiling. The oil passages are internal, and aren't accessible from under the side cover. The 216's and pre-1955 235's had an oil line under the cover, but it was a PITA to deal with- - - -impossible to remove without destroying it as it went all the way through the water jacket and was secured with one-time-use compression fittings. You can remove the 1/8" pipe plug at the center of the cylinder head to see if you're getting oil flow there.
Jerry
