After getting spammed for hours with infinite messages and missed calls which were mostly made of threats about bad reviews I go back home and open my wallet to see that there is nothing in there.
This should have been a red flag. In peer to peer trades, you should never feel rushed or harassed by the other person. Whenever you do, it is usually because they are trying to pull something shady. In this case, he was rushing to get you to send your half of the trade before his transaction confirmed, so he could replace it with RBF and steal your money. However...
Mutual characteristics between the 2 accounts.
I am not convinced that any of the characteristics you have listed are enough to make a definitive link between these two accounts. It seems to me that there is a not insignificant chance that you have just stolen $500 worth of bitcoin from an innocent third party.
There's much more than that going on in this case. Say for example, how high are the chances that someone will pay a 5% fee for a crypto <-> crypto exchange when they can use KuCoin to do that for a much lower fee? There's just too many things going on with this one. I am still verifying the transactions tho and I am going somewhere with it, like the scammers address being connected with the second persons address. Still needs much work but will post results when I'm done.