Advice is best when it gives you insight to make your own decision. When you ask a specific question, to split or not split, then I'm unsure anyone who answers that directly, will have done the right thing. I believe you want to avoid the decision by getting someone else to tell you what to do, which is understandable, but not really the way to go.
woofgang basically sums it up.
It is clear there is no way both your wishes can be satisfies, one has to let their desire go for the other. And having had a row over it already it looks as if you are getting further apart on the issue not making progress.
You may try to talk calmly over the issue and listen to each other's point of view, but ultimately if he doesn't want children (at least yet) then you should not force it. IMO a child is more likely to be a continuing issue for the future than a change of heart.
If the fact that the clock is against you so if he wants kids at all he should bring his schedule forward does not convince him, then best consider whether you would prefer to give up the desire for a second child, or would prefer to make the break and find someone who is interested (preferably in you as well as interested in having a child by someone).