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

In my experience, if an engine has more than 60 thousand miles on it, once coolant or fuel gets into the oil system, the bottom end will come apart within 12 thousand miles.
Main bearings are made of a Babbitt lead material. Its wear smears to voids making it sort of self conforming, almost self healing. Water or gas will wash that material away.
The 7 quarts of oil had to go in one of 3 places.. in the coolant system ( unlikely ), in the cylinders, or down the exhaust pipe. I hate to say it but it really doesn't matter where it went now that we see the fluid mixing.
I would pull the head and rotate the bottom end to inspect the bores. If I didn't find a wrist pin walked, or a cracked cylinder wall, I would assume for now that I have a rebuildable engine.