I Need To Know If We Can And How To Sue A Former Employee For Wrongful Termination And Defamation Of Character?

My husband has had his driver’s license for ten years and his cdl for just over a year now. He has worked for a major over the road trucking company since February. Maintaining a safe driving record for over 500,000 miles. He was involved in his first ever minor rear end collision about two weeks ago. The scenario of the accident was as follows: on an interstate, traffic had slowed to a crawl of about 15 mph and my husband was following two other semi trucks, he had a gap of about 6 seconds between him and the truck in front of him. The brake lights of the truck in front of him were not on when my husband took a few seconds to check his mirrors and traffic around him. When he looked back the truck in front of him was stopped and my husband locked up the front axles of his trailer trying to stop. He hit the trailer of the truck, that truck was so close and had stopped short causing the accident, that he hit the other truck in front of him. As a result of the accident, which no one was ticketed for, the company my husband worked for fired him. Now my husband leased his truck with this company, so we do not believe that they could fire him but merely terminate his lease, which for truck dirvers is two different things. Well my husband has been trying to get another job and everyone has turned him down and we couldn’t figure out why until today. One of the potential employers finally told my husband what was on his DAK and the former employer has lied and ruined his record. They put that in February he hit an animal, which he didn’t, he hit a tire tread in the road because he was surrounded by cars and had no choice. And then also in February when he was home a women hit his parked truck in a parking lot when my husband was no where around, again not his fault! These two incidents should have never been put on his DAK and then to top it off they put that he was fired due to a rear end collision and disqaulification to haul thier loads and that he had a very poor safety record. The accident is true but the rest is not. My husband was a driver trainer for this company, he trained more than a handful of their current employees in the ten months that he worked there. If he had such an aweful safety record then why would they allow him to train other drivers. This company has temporairly ruined my husbands driving career. He is a third generation truck driver and a college educated man and this is what he loves doing and they have maliciously taken this away from him and for what. What are they getting out of lieing and ruining someones life. He never once talked to anyone in the safety department about anything until his accident and his safety manager was an a complete asshole to him. We live in Tennessee and the company he worked for is based out of Salt Lake City, Utah. I want to know what we can do legally to fix this and to make this company pay for the unjustified damage they are causing to my husbands career. Does anyone know what we can do? Can you please point us in the right direction? And can this be done at no cost until the end? They are also holding all of his pay which they say is legal in thier state of Utah. So we are behind on rent, electric and other bills and we have a two year old son. So time is of the essence. Thank you so much for your help.