If you have friends or relatives living near you, it might be a good idea your daughter lives them for a while, at least until something constructive can be sorted out over this issue. You can also speak with her about what she wants and decide how to approach things from there.
If your husband has no problems with your daughter other than her being a step daughter alone, then at least one positive sign is that she is not to blame for anything. Perhaps your husband can speak to someone such as a scholar, a learned person or maybe even a understanding Imam.
As it is Ramadan, your duas are more likely to be answered now that at other times, especially as you are in a dire situation. Ask Allah and He will prepare a way out for you inshallah.