So, I left the car to a very good mechanic last month who has been trying to solve this problem. He started going through everything I had already done and some more.
He says there was garbage blocking some coolant passages which he found after pressure testing it. Unfortunately he says that the block is cracked/rusted through somewhere as well..
This makes a lot of sense to me, the way it was overheating regardless of running conditions implies it is not a fan issue for example.
Thanks for the help!
