All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
We have already issued Fatwa 84618 clarifying that, in principle, the fostering is for the mother as long as she does not remarry; so please refer to it. According to the preponderant opinion of the scholars if the boy reaches the age of seven, he is given the choice between his parents and he will be with whomever he chooses amongst them.
As regards a girl, she should be given to her father on the condition that he has a wife or a female who is suitable for fostering; for more benefit, please refer to Fatwa 87762.
However, if we presume that that child chose his father, it is not permissible for the father to instigate him/her against you as this is urging him/her to cut the ties of kinship with his/her mother.
Moreover, the jurists stated that it is not permissible for the parent who is entitled for the fostering to prevent the other parent from seeing the fostered child; for more benefit, please refer to Fatwa 84575.
Furthermore, your husband has to spend on his children who have no money as this is an obligation on him and it is not permissible for him to be negligent about this. Nevertheless, even if he did not spend on them, this does not waive his right from fostering them.
With regard to your husband spending on you after divorce, then if this divorce is revocable, then he is obliged to spend on you as long as you are in your waiting period. If your waiting period expired, then he is not obliged to spend on you. If the divorce is irrevocable, then according to the most preponderant opinion – which is the view of the majority of the jurists – he is not obliged to spend on you unless you are pregnant.
Finally, it should be noted that if it is possible for you and your ex-husband to reconcile and forget the past, then this is good, otherwise it is better to reach an agreement through some righteous people far from the courts just in order to respect the feelings of your two children.
Allaah Knows best.