wtf ya been doin' Wrangler?!?!?!?!
In answer to your question, none of your scenarios would happen (do you really play this game at all?) - if you sell him, he doesn't go back to his previous owner (that would never happen), his card pretty much lies in limbo unless someone you are friends with is also friends with him. They can buy him with all his skills (such as they are) and you'll get your $8 mill minus Top Goof's cut.
If you let him go to poach someone will buy him and you'll get your dough as well.
Now - to more important business! Where in the HELL is the Round Table you were to have provided months ago??? Get to work!