Stepson lies to school counselor and srs about being abused. What should I do to protect myself in the future?

My 12 years old stepson was prompted by his mother to tell his school counselor that " we fight, throwing things at each other while he hides in the closet shaking". That resulted in SRS investigating child abuse. Mother of the s.son did the same thing before when he was 3 to another woman who was with my husband at that time. I feel humiliated, violated, and similar to what a victim of would feel. S.Son lives with us half of the time. He is extremely spoiled and hard to deal with as it is. Now I cant even bring myself to be around when he is around. I come home when he is ready to go to bed . I know it could happen again, and I will be at the mercy of a social worker.I will lose my job if the"abuse" is confirmed. No one is abusing this kid, his father loves him and spoils him, I am nice to him, but I am strict- i make him clean his room and make his bed with no rewards- this is his responsibility. He also has to walk the dog. This is not too much to ask. He is a picky eater- he once was throwing out bacon out of my mashed potatoes on the floor! because he didn't like the taste. It is insane but we were dealing with this together with the husband. Now I feel like I don't want to deal with it anymore.I don't want any interaction with this kid. Clearly the situation cannot continue like that. HE will live with us until he is 18. Any suggestions how to get out of this situation short of divorcing my husband who i love?