I am childfree so admit find your attitude frustrating OP
You can't compromise on having a child. Not wanting more means just that - not procreating again.
That doesn't mean you wouldn't consider being with someone who has their own children & it doesn't mean you wouldn't actively engage with a partner's child - but they are still not your children. He had no parental responsibility, he did not seek to adopt these children. He just accepted them as part of a package deal within that previous relationship.
It's being so blinkered to assume because he was kind to his ex-partner's children & helped her with that that he should give you a biological child.
To say he doesn't love you enough to give you a child - when people decide they don't want more/any children they want to preserve their life as it is - their world is enough for them & they don't feel a need to create new life as some "symbol" of love. We all know having children is like setting a bomb off in relationships & many relationships don't survive the stress that having children can bring.
So he is actually saying he loves you for you not what imaginary child you could provide & he is content with life together as it is.
Being childfree isn't about not loving someone enough - it means you don't want the responsibility or burden of more children personally. It doesn't mean you don't enjoy other people's children.
This relationship is over - on the childfree boards we see this same story play out all the time. You got together both hoping the other's opinion would change & it was too early to have those lifetime commitment discussions. But you've reached a point where you have decided you definitely DO want kids & he has decided he doesn't.
Nobody is wrong, it's just an irreconcilable difference in how you view your lives & futures.
It's hard but you need to prepare to leave now - he sounds like he has been a stand up person & not trying to string you along or waste your fertile years. He is being upfront, so it's time to say your goodbyes & look forward to the future with someone who also wants to start a family one day.