Let me just start out by saying you to need to go into couples counseling if you want your relationship to work.

However let me address a few issues on your end...

In my own words I said "I would rather know now if you, for example, wanted to wait until you're 35 to have kids, because I probably couldn't stay in the relationship.

Put yourself in his shoes. You just told someone you say you love that if you don't get your way (having what would be his kids just as much as they would be yours) you're going to leave him.

Imagine how that feels, he's clearly not ready to have kids or afraid for whatever reason, but you're telling him if you don't have your 1st kid but a certain age you're leaving him. That's pretty screwed up. However, relationships are all about compromise and that means you too have to compromise in you both don't see eye-to-eye.

I think their is a time and a place to talk about having kids, starting a family, life goals, etc. and you missed that mark a long time ago. You should have (casually) discussed it in the first 6-months so not time was wasted on either side.

Again, I strongly recommend you get into counseling simply so you two have a mediator. There you might be able to express your concerns about why you want feel you need to have your 1st kid but 35 whether that be because you're afraid of "being too old" or fear of a drop in infertility, etc. regardless your reasons why you feel the need to have a kid by 35 "or else" you'll leave him needs to also be address in this counseling process. You can bring his your concerns you have his issues and they too will be address in therapy.