This seems all messed up by SMARTMIXER.IO besides 10
BTC is a good amount of money to exit scam for small businesses.
(screenshots, guarantee letter, records in the blockchain, I can provide the private keys of the address from which it was sent, I can sign the message through the address, I can provide email logs, I I can provide access to private messages on the forum, I CAN PROVIDE ANY INFORMATION REGARDING THIS ORDER)
Guarantee letter should be enough.
You do not need to give the private key of the address, you can just sing a message using the address to prove the ownership of the address if necessary.