A question that I am not sure how to even ask...

Hate to say it, but that engine needs to come down. That "broken collar" is called a core plug. It's been leaking coolant into the valve cover area of the cylinder head. That's going to have to be removed and replaced. Only way to get that out is to remove the head and get it to a machine shop to be drilled out. Or you could replace the head. But the milky looking substance is where coolant has been leaking from it. Now, about the engine oil. Is it remotely possible that since it's fresh oil that you simply are not seeing it on the dipstick? Have you held it in the light good to try to catch the reflection? Stranger things have happened. The head actually looks pretty clean. No chance the oil drain back holes are plugged there. Can you shine a light into the pushrod holes and look at the oil return holes in the block where the lifters are? See what that looks like.