Is the husband's threat to abandon his wife and child if she refuses to stay at her family's house, and to withhold her maintenance, and to insult her and her family, along with the ill-treatment of the husband's family towards her, considered a termination of the marital relationship?

You are not obligated to obey your husband by staying with his mother, and he has no right to force you to do so. The husband is obligated to provide for you and your child according to what is customary. If he says to you, "You are no longer my concern," and he intends divorce, then it has occurred; otherwise, it has not. Discuss with him the obligation of maintenance and living together in kindness. If that does not help, then let two arbitrators intervene to reconcile between you.