Blackballing

Here is the short version of this situation. I am a mortgage broker in Columbus Ohio and have been for the past 7 years. I have recently left an employer on bad terms due to me holding a funding check because I was told I would not be paid on it. From what I have read, it is legal for the employer to give any information as long as it is true, and I understand that on a reference check.

My question to you, is it legal for an employer to find out where you are currently working and contact them to share this information? I have already gone through 3 employers in one month due to my prior employer finding out where I am and contacting them. I have two people, one from a title company and one from a lender that told me my old manager stated that "Ken would never work in this town again and that the owners of this company are very good friends with the owners of the company Ken went to and his job won't last there long". Four days later I was fired from the new company and told "This company just isn't a right fit for you Ken". I have since been contacted by the person that was in charge of my background check telling me that he never did the check and he was told by the manager in a round about way that the owners made him fire me.
I then went and obtained an agreement from an old friend that owns a local company to work from my house at a very high commission rate (75%). Three days after that agreement was made he called me concerned about a phone call he had received from a person at my prior employer. Again he had not done a background check and had no intentions to. He was contacted from someone from the prior company in attempts to blackball me from this industry. Needless to say he canceled our agreement.
This is a very close knit business in Columbus, and everyone knows everyone. Even if I get the company to stop this harrasment the damage has been done. They have told everyone that walks in their doors ( Lender Reps,and title companies) this information to insure that it keeps me from working in my industry. I do not know what to do at this point I have gone from making 6k-13k a month and being a well known producer in this industry to being blackballed,, is there anything I can do?