How should I deal with my husband, whom I found to be in possession of sorcery and who is negligent in prayer? And is my staying with him forbidden, despite his good treatment of me?

You must explain to your husband the seriousness of dealing with sorcerers, soothsayers, and charlatans, and the seriousness of being negligent in prayer. You can give him tapes or booklets that discuss this.

Your husband's going to sorcerers is not major disbelief unless he considers their actions permissible or believes they know the unseen. In this case, it is not permissible for you to remain married to him. However, if he knows their falsehood and that only Allah knows the unseen, then this act of his is minor disbelief, and you are not obliged to separate from him, but you are obliged to advise him.