Is it permissible for a wife to return to her husband after three years of him abandoning her and not spending on their child, and after he forced her to abort the fetus and his family mistreated her?

It is permissible for the wife to return to her husband. If she agrees to return, then reconciliation is better, as Almighty Allah says: "And if a woman fears from her husband nushuz (ill-conduct or desertion) or aversion, there is no sin upon them if they make terms of settlement between themselves, and settlement is best." If she fears the continuation of ill-treatment, she has the right to seek divorce. If he does not respond, she can refer her case to the court. She also has the right to demand what she spent on herself and the child if it was with the intention of recourse against the husband. The ill-treatment by the man and his family is a religious transgression, and abortion is forbidden at all stages of the fetus, and it is an unlawful killing of a soul if it is after the ensoulment.