Oh wow, TAL I am so sorry. I soooo know the feelings of hurt and anger at your son's party, because of your H's behavior. Something is up. Something. I wish I knew what.
The toy thing is odd. Did he seem like he was 'busted' when you said the immediate look of guilt?
Here's the bottom line:
He is hurting, and hurting you. You are not overly sensitive.
He was extremely selfish and insensitive at your son's party. You were not over reacting.
Something is going on.
I wish I knew what it was, and could wrap you in bubble wrap so you don't get hurt again.