As far as being the worst mother in the world goes. How could you possibly remember and maintain awareness about allowing your son to drink after you? You had no training or warning that these things could happen. It took me years to get into a routine to not cross-contaminate and I did not have the busy life of raising children.
Humans living a normal life have no idea of the monsters that live in our world and can harm us.
You did the best you could and if it's any consolation I dont think it was the drink that infested your son. My friend's partner was infested by him just though touch.
Your stress is coming from the lack of belief from your husband and the need to protect your children. Someone needs to step in and tell him he is being an idiot. Somone needs to be your hero. Maybe send him the link to this forum"" or get a man who is forceful to speak to him. Someone he will listen to.