I'm thinking the bearing failures were due to some foreign material getting into the head when the VCG job was done.
An brief intermittent oil pressure issue probably wouldn't result in the amount of damage that you have. More likely, the disintegration of the bearings lead to the intermittent oil pressure problem. Bearing #3may have lead to the failure of #4 or both may have been subject to some foreign material.
Whether the problems are independent or related, you still need to do your due diligence and investigate every bit of the engine that you can for additional damage. Drop the pan as others have said - you have to take a look. You may also want to do compression & leak down tests to determine the health of your cylinders & valves - those metal flakes seen in your pictures are very disturbing - who knows what bits have traveled where in the engine at this point.
Also check the entire oiling system. Look for debris in the pan, the oil filter, everywhere!
You have a lot of investigation to do before you even consider what direction to go in.