I'm glad you went to the competition. I'm sure your Ss16 was happy to have you there to watch him dance. Kids need to know that their parents (and step parents) are there supporting them.
As for your h...let him twirl in the wind. He is losing out on so much.
Julie, give yourself a break. You are going to have days when things trigger those emotions. It takes a long time to heal from this type of crisis. Feel the emotions, allow them to wash over you and then release them.
One day, when you least expect it, you'll discover that those triggers won't affect you as they have in the past. It all takes time, i.e., one day at a time. Don't rush the process.
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.