Unless it's in writing, unfortunately, it's your word against the Realtor's. You can't sue the Realtor, but you can sue the contractor for shoddy work. The Realtor merely referred the contractor to you.
In most places, you do not have to have a business license or a contracting license to do small jobs..and $1500 is a small job, unless it is structural.
What kind of legal issues were holding up the settlement? You didn't say...we would also need to know what "went wrong" with the previous repairs.
Construction, like beauty, is in the eyes of the beholder. What one contractor considers quality work, another will trash...especially if he or she is trying to get your business.
You cannot sue for the failure of the home to sell, b/c it doesn't appear the legal issues had anything to do with the repairs.
Feel free to e-mail me if you have more questions.
My full list of credentials is on my profile.