I do agree with a lot of the comments quoted.
To be blunt, you have 2 children who need you already. You have said you want to leave but cannot afford to. What if there is a baby thrown in the mix? I just think it would make it harder to leave and then how will this affect the children?
Another thought is if wanting a baby is just trying to fill a void. I support women and men wanting and having children when single - but they need to do it for the right reasons. If you truly believe this is right for you any opinion we will have will not sway you. I do hope you make a decision that is right for you and your family.