My agreement went in stages; maybe you can try that. Say that you want it this way until S is 6 years old, and then you will alternate. So far my wasband has never taken all the time he could and has missed many holidays we were to split. It's possible that his desire will fade and he'll forget by the time S is 6; if not, you'll be less raw then and can figure out a fun way to make it through that night -- maybe by finding a family in need and helping those kids on X-Mas morning!
Splitting the kids is horrible. It's why we were standing. Your feelings are right. But it's best to make a deal as a judge could give you less. If things go badly you can always fight for a custody change a year from now, when you have lots of records.
I believe I will see the bounty of the Lord in the land of the living. Wait for the Lord with courage. Be stouthearted, and wait for the Lord.