If he really wanted to, he would just have to wait until brick-and-mortar stores or online stores accept BTC as a form of payment and he could spend those BTC directly there, no need for selling them first.
There are already many stores online and in the real world where he could spend his coins. Regardless of that though people would go crazy as soon as the coins moved anywhere and would spend a lot of time trying to trace them. They then likely would be able to be traced to the stores he used them at.
Wouldnt that require knowledge of the store's wallets? As far as I know, many of the brick and mortar businesses simply use one of those bitcoin readers that automatically transfers the bitcoin based on a customers wallet.
Huh, what do you mean by "Bitcoin readers that automatically transfer the Bitcoins based on a customers wallet"!? I think many stores simply have a single address, maybe have the QR code for that address printed out so they can show it to the customer, who can then send the coins with his/her mobile phone. Online shops of course have to use changing receiving addresses, otherwise they couldn't successfully discern between different customers' payments!