In my past I have battled addiction and all of the evils that come with it. In July I stole some furniture that I had in my house, that was property of my in-laws. I sold it to a local auctioneer. Within weeks my wife made arrangements to buy back half the items, which I appreciated. Today (Novemeber 10) I was at the auction and spoke to the auctioneer about buying back any left over items. He stated that on November 20 he is having an auction and that the one remaining item would be sold there and that was my chance to buy it back. He knows that it is stolen property. Do I have any angle, like to get the police involved?

You could report him but you will also need to turn yourself in. Sorry to put it this way but he knows its stolen so he's breaking the law but you are the original thief. If you want to stay out of jail go to that auction with a pocketful of cash, I am sure he won't take your check.

The owner of the property, with proof it is theirs an come with the police after they have filed a stolen property report and claim it. He will have to turn it over to the police as evidence .

He knows it is stolen because you told him?

Yes if he knows he could be arrested, but after you are normally. And you will get far worst punishment than he.