Okay, so you want another child and he does not. First of all, is that a deal breaker? Can you still love him if you don't get a 2nd child??
Second, play an imagination game with me. You were a SAHM, but now you have a 4 year old, an infant, and a divorce, so you are now a full-time working mom, with 2 outside careers to keep the $$ going, and no time to play with either baby. Deal breaker?
You said you would "do everything" so he would not have to do anything additional. MOMMEEEEE, I WANT A PUPPY!!! (tears) I WILL DO EVERYTHING FOR IT AND TAKE IT FOR WALKS AND ......
(sound like any child you know?)
I'll bet that your husband just wants more time with you!!!! With his jobs and a 2 year old, it is probably hard to get time together, let alone the $$$ for an additional child. He may not want to take a 3rd job to support you, you will have to get a job, nobody can stay home with the children, you are both too tired to enjoy each other, etc. etc. etc.
Back off from the discussion for a year, then revisit the question. My kids are 5 years apart, you can survive that gap. But if you make a big scene now, your marriage may not survive the big scene. And he would resent the baby you "talked him into" having. And it is NOT FAIR for a child to be resented like that!
PS - your surrounding family DOES NOT get a vote as to the size or timing of your family!!!!
Good luck with your decisions. Cut your husband some slack, and you too. Just enjoy this child. There is time in the future to make further decisions.