Now, I would sit right back and not mention divorce again.
I (kinda) disagree here. Only because of your financial situation. I would consult an attorney and figure out what you need to do to protect your financial interests. Sometimes that involves filing, sometimes not. But do what is in the best financial interests of you and your child. If he's benefiting financially by not filing, it could take a very long time for him to file.
AND NO LBS SPOUSE EVER GOT THEIR WAS BACK BY NOT FILING. Being a doormat or letting them take financial advantage of you has never brought one home. And the ones who want to come home will do so whether you have filed or not.