How do I know this is a scam?
Here:
He will send you a link asking you to prove to him your funds are clean, that website will ask for access to your Metamask or w/e wallet you're using, once you do that, your money is gone.
I understand that but he can still share that "scan" link of his for us to check. If he does that then we will have definitive proof but I don't think he will ever come back. In my experience, 100% of the people who have sent me these "scan for AML" bs links have been scammers.