OP
You haven't really gone into how the rest of the relationship is, or how you feel about your partner generally. So I'm going to assume you were relatively happy at this point.
I would, as coldly and business-like as possible, do the sums on your finances without him, including the child maintenance he will be obligated to pay.
Show him these figures. Explain that he would have the option of being a weekend or 50/50 parent but would be obliged to cover all the child's expenses during this time.
Make it clear that you 100% expected to return to your FT job, he agreed. Be clear that if he sabotages that goal, you have no choice but to evict him, as this is a very important agreement to you, a deal breaker. You expect him to be a fully invested parent, otherwise you may as well do it alone.
I realise the above is a big risk, but I think it's in your interests.
His response to this move will tell you all you need to know. He will either roll over, explain him position better in an attempt to negotiate, but still roll over, or leave, with or without extended arguments.