No wonder he was angry.
If he wishes he could claim reliance damage. However, the key is good faith. He must prove that he actively looked for another house but was unable to find a similar house within a raesonable time. He must also prove that he actively tried to secure a loan but could not get anything below what he's gotten right now, within a reasonable time. If he is sitting idle no court will allow him to recover anything. Other than these, his recovery would be limited to the reasonable and foreseeable expenses he paid, such as document fee and maybe fuel expenses. Since the expenses will not be involved with a huge dollar amount, I don't think any lawyer would be interested in a case like this. In contract case emotional distress is not recoverable. Nor is punitive damage. I think the guy is bluffing.
To make sure, consult an expert, who is from the realtor company and who is familiar with the realty law.