Also wondering if I'm taking on any legal risk by participating or not participating? 

or contracts from places like legal zoom good enough?

Do not rely on it as legal advice.

He knows how it works, and he's creative enough to find ways to legally do things.

I assume a simple short message on legal pad yellow paper in an envelope would do it, but what about postage?

I certainly see why you would be upset but I don't envision there being a legal avenue for changing the outcome.

Hope that is still legal.

What's the terms of your agreement; how many days do you have to assign your contract, what happens if you don't find an assignee, do you have a legal and air tight assignment agreement, are you legal (not acting as an agent), is there real consideration, how much and who is holding it consideration, do you have a built in extension in the event you don't close in time, do you have right of possession durning contract period, what showing arrangement do you have?

I recently learned that I can't legally charge a management fee in state of Oregon for "managing" a small residential property.

Are the double closings/simultaneous closings legal in CA to be specific?