Re: feeling alone
The first issue I would address with DH is, he is either with you or against you.
My DH "refused to take sides" for years until he realised that by not taking sides he was siding with his sister. Reason being, I never do or say anything to her. I just keep quiet. She is always attacking me so by him remaining neutral he is allowing her behaviour.
Your DH needs to understand that you are coming to him out of respect for him and his family. Tell him you COULD deal with it yourself but fear the ramifications of doing so. Maybe he will then decide to speak to his mother rather then let you suffer in silence.