"And I didnt say I didnt know what it was like to BE a child...I remember being a child very well. It was misery (i had a bad time) I feel sorry for him, because Ive been there(minus the spoiled thing)."
Childhood = misery, therefore a child is miserable, hence the non-maternal connection. Makes sense to me.
Entering into a partnership of convenience has its pitfalls. You have made your position on committing to this man very clear: no committment, only convenience. If this is the core of your partnership with this man, I would urge you to END IT and avoid getting into such a situation in the future. This kid didn't make himself - he is the product of a couple that were obviously not emotionally or physically prepared to have and raise a child (a more-common-than-not scenario, these days). This kid doesn't have a choice in any matters affecting his emotional or physical health - he is at the mercy of whatever suits his mother and/or father. Having said that, he is not your responsibility and, under no circumstances, should you be made to feel that he IS.
If it were me, I'd get the heck out, pay off the lease or make some arrangement, and never enter into another arrangement of convenience without taking the entire picture into consideration, again. Just my 2 cents.