Can my husband sue me if he gets fired for me telling his boss about and office affair?

No, your husband cannot sue you.  However, his lack of employment may affect issues such as child support, alimony, debt division, and the like.  This is particularly true if it will be difficult for him to obtain another position that pays as well as his current job.  If you are divorcing, it may not be in your long term financial interest for him to be terminated from his job.