You really need a PCV valve on one side that's actuated by engine vacuum. I put PCV valves on the passenger side of my engines with breathers on the driver's side.
One thing you could check is to remove the valve cover and take a look at the valve seals on the #5 cylinder. They are hard to see through the valve spring, but you should be able to see if something is badly wrong.
Otherwise, my thoughts are that you have a piston ring issue on that cylinder. You could put compressed air into that cylinder (part of a leakdown) and listen for a great amount of air entering into the
oil pan.