BB, Shining gave you excellent advice. If you say anything to him about being discreet, he's going to ramp it up because he doesn't care about what you want...but more importantly the only person he's worried about his himself. He's acting out and the more you point things out to him, the more he's going to do what he wants, i.e., you are right now the mother figure to his inner child.
You don't have to stress yourself over decorating for the holidays. Do something simple, make new tradition, i.e., keep things simple for you.
When the pain hits, feel it, allow it to wash over you and then release it. You are human, and yes, there are going to be days when you don't feel up to doing anything. Always remember, there's always tomorrow if I don't get it done today.
Take care of yourself and take some much needed time to pamper 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.