Is going to court to settle a dispute over inheritance considered a sin and a severing of family ties, given the existence of bargaining and manipulation on the part of the other heirs?

We advise you to be kind to your stepmother and maintain ties with her, for that is a way of showing piety to your father after his death. However, this does not mean waiving your right to inheritance. Ask people of goodness and knowledge to intervene to divide the inheritance according to Islamic law. If she remains obstinate, then there is no blame upon you in resorting to the judiciary; for a son suing his father to obtain his right is not considered disobedience.