I am so very sorry that this year he was not able to wear the mask for very long, if at all. Sounds like he was miserable and didn't know how to relate to people being happy. So very sad.
I am glad you were able to enjoy the holidays in spite of your h's behavior. It's difficult at times to deal w/someone who is so very depressed and doesn't know how to dig himself out of it.
As for your MIL, she doesn't get it and most likely will never do so.
I'm sure you will enjoy traveling and being away from the "madness" for a while.
Wishing you and your family a far better year than the one that is ending.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.