Step relationships are hard. Even though you are working in the mental health field...find a trusted psychologist and start therapy. Later, you might feel comfortable adding your husband, if he will be open to this.
So the boys mom is still homeless? Why isn't there shared custody? I think the school counselor would also be a good place to start getting help. Does he have an IEP? Would your husband listen to them and try to get him help? As a step parent, you have very little rights and authority to do anything.
Please keep us updated. Newksm