Would we be wise to continue action for slander and or defamation of character?

My husband was recently fired over two events involving "hear say". He was accused of damaging a part that was welded by another employee by pouring water on it. They claim they have a witness who saw him do it and he told someone. He was also accused of threatening to kill his boss. For this one they claim someone heard him say this. For the first one, my husband did admit he did say (to one person who he knows who it is) "Yeah, I should pour water on that part." He joked and never did it. The part was not ruined by water damage and the part was sent out without any damage and has not been returned to the company damaged. The other thing my husband knows he didn't say. He got fired over this and has no write ups in his personnel file. Now it is spreading around other business that Tony is damaging parts and threaten to kill his boss at other business he is trying to get jobs at. Even places he has not put in his application know this information. He lost his job for "hear say" now this is spreading like wild fire as if it is the truth. My husband has no criminal record or even a speeding ticket. We think, but are not sure, that the person that Tony said he was going to put the water on the part, is the one who told about him wanting to kill the boss. This same person has also been text messaging my husband since this began and my husband has asked him to stop communicating with him. He can not find a job, this is ruining is repuation and character, ablity to find work, not to mention our life. Can anyone help us, this is so unfair?