It gets better. Next year will be your choice and you will make new traditions.
Everything will get better. Some of it will take more time than other things, but you are liberated from his control and can make your own decisions.
With respect to him being unavailable tomorrow, is this the third or fourth time he has not been able to keep the arrangements? This is now a pattern and has previous PPs have suggested, a solicitor's later would probably be appropriate.
I wouldn't offer to change, just state that you have both agreed the arrangements. Then list the times and dates when he didn't keep his side of the agreement.
Then restate the arrangements and say that you expect him to drop off/be there when you drop off on the xx date.
You may wish to get the solicitor to list the expenditure as well, the mattresses, the school uniforms etc and expect him to pay half.
Even if he ignores the payment, it is in writing and becomes evidence for any mediation and court hearing. It's part of the grey rock.
You are amazing. And we love you.