Kudos to you for being smart & doing pre-marital counseling, so that you can start things out on the right foot.
I'm sorry your DF is sticking his toes in. The big thing to do is to apologize for hurting his feelings. Clearly, he felt attacked for what he probably thought was an honest mistake or misunderstanding.
So, the best thing to do is to apologize. You could say something like "I'm sorry our disagreement got out of hand yesterday, and that something I said really upset you." Wait for acknowledgement of this. Or, if you're not sure what you're supposed to be apologizing for, ask him (nicely); maybe say something like "Things got out of hand yesterday, and you said you wanted me to apologize first. I just want to understand the transgression so that I know why you feel wronged." (or something like that).
Once you figure out what he wants you to apologize for, even if you don't agree that you did anything wrong, you can still apologize for his feeling hurt/attacked/whatever, and tell him that wasn't your intention. Then, ask him how it would be better to bring this up next time, for example, if he did feel attacked about your comment about the plans next week. The key to avoiding it is finding a way to communicate in such a way that you aren't pressing each other's buttons and setting each other off.
If he doesn't apologize for the name calling, in a couple of days, bring it up as a separate thing from the apology above. Tell him that while you understand that he was upset, that was crossing the line in your relationship. And that if he feels that he's going to be that upset, then you two need to find some way to get breathing space and cool off before continuing the discussion. Ask him to help you solve this issue, rather than make it an ultimatum or rule dictated by you.