What an awful situation. I would be devastated too. He has gone about this horribly. I would ask to have a reasonable conversation & come to a compromise. You said your DS is 4 months & you were planning to return to work anyway when he is 13 months. Could you compromise by waiting 6-10 months for his back surgery, &you return to work then? Then if you feel uncomfortable with MIL looking after your child, you could use daycare (or whatever you were planning on doing when you did return to work) while DH recovers & hopefully returns to a place of being able to work again? Sorry yoi are going through this. What a tough time for your family.