I think it is perfectly understandable that you are feeling so down. It is so natural that you should be so upset by your dad's unhappiness. But deep down you must know that he is in the right place and, as people have said and as we often read on TP, people do settle down in care homes even though the initial period is, for many people and their relatives, traumatic.
As for Christmas, it's just another day. There will be other Christmases. Perhaps you should think about all the things that you enjoy doing but have been unable to spend much time on whilst you were caring so directly for your parents. Maybe you could try to revisit some of these over Christmas.
It makes sense, as others have said, that your husband is trying 'tough love' to help you to see that you have done the right, and only thing. Maybe you should, as suggested, talk things through with him - if you can. Though you must have had the main caring role, I don't suppose this past year has been a very happy one for either of you. But now that you at least have a little more time to yourselves perhaps life will gradually start to look a little bit brighter. I'm sure all who are reading about your situation will really hope so.
Stay strong.