Kimmerz, His mood swing could very well be the holiday coming up...after all, it is a family holiday. Think back to the other holidays and try to remember if he had mood swings prior to them as well. Many of them will get this way before a holiday, event or anniversary of something special.
There is absolutely nothing you can do for him. No matter what you do while he is in crisis, he will not be happy. Devote your time and energy to your children and on yourself.
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.