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, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Indeed, you did well by not obeying your husband when he ordered you to abort the child because abortion is forbidden as we clarified in Fatwa 82051. So, may Allaah reward you.
As regards your questions, the answer will be in the following points:
1- It is an obligation on the father to spend on this child. If he refuses to spend on him, and you find that he has money, it becomes permissible for you to take it from him to spend on your child even without his knowledge. Besides, you have the right to ask your husband to reimburse you the money that you had spent on your child prior to this, if you had not spent it on him as an act of charity. For more benefit, please refer to Fatwa 85012. Rather, you may also ask him to reimburse you for what you spent on yourself and which he did not pay you before divorce and after divorce throughout your waiting period unless you had renounce this spending from him or that the divorce is irrevocable.
2- The spending on the child should be according to a sufficient spending while taking into consideration the circumstances of the father; Allaah The Almighty Says (what means): {Let a man of wealth spend from his wealth, and he whose provision is restricted — let him spend from what Allaah has given him. Allaah does not charge a soul except [according to] what He has given it.}[Quran 65:7] Nonetheless, it is the Muslim judge or whoever acts on his behalf who determines the amount of spending. Moreover, what the wife earns is her own money and it does not affect the amount of spending on the child that is obligatory on the husband.
3- When the wife remarries, the right of fostering the child moves to the person who has more right in fostering him after her among the females, like the mother of the mother [grandmother of the child from mother’s side] as per the sequence that is mentioned by the jurists ; this is clarified in Fatwa 84618. We clarified in this Fatwa that when the child reaches seven years of age, he is given the choice to choose between his two parents. If your son has a foster parent, then you have no right to ask to foster him after you have remarried another man.
4- You should not refrain from remarrying especially in this day and age where there are so many trials, and you need a husband to protect you. Marriage is something obligatory when a person fears being subjected to trials [tempted to commit illegal sexual intercourse]. Moreover, the fostering of the child is only given Islamically to the person who would care about his benefit and Allaah The Almighty will protect him for you, Allaah willing. The fact that your son is with someone else is not an impediment that would prevent you from seeing your child and visiting him from time to time, and the like.
Allaah Knows best.