Must I remain with my mother, with my wife serving her, to avoid disobedience? And if my wife is prevented from serving my sisters and their children, and I suffice with normal kinship ties, then what is the ruling on that, given my mother's increased displeasure?

You are not obligated to keep your husband to serve your mother, your sisters, or anyone else, and you are not considered undutiful to your mother or a severer of your ties of kinship by doing so. However, you must be dutiful to your mother and treat her with kindness. You should combine being dutiful to your mother with treating your wife well, and not burdening her with what she cannot bear or obligating her to what is not incumbent upon her.