Husband taking a Christian as a second wife and ill-treating the first wife

Q:

1. My husband married a Christiam girl who didn't convert to Islam. Is the nikaah valid?

2. He stays 1 night only with us and its affecting my children now. Is this permissible? He treats me, as a first wife, very badly. He talks rudely to me and is always angry with me. His 2nd family is always treated well.