Well, DH and I both like to giggle at BM's obvious misery in the form of not aging well, looking frumpy, achy and awful.  And she also tries a little to get attention, but honestly we don't see her much anymore.  Once he went to pick up SS recently and BM just had to go out to her car at that very moment that he was in the driveway.

We joke about it and move on. My DH would not piss on her if she was on fire.  Are you implying your DH still has feelings for BM?

Tell him blasting you is not ok, dredging up all details of BM during special day for SS is not ok. He needs you to bop him over the head with how that was NOT OK. Even not being the jealous type, IDEFINITELY have boundaries when it comes to Toxic Troll, my DH ex. She has crossed, disrespected, and trudged all over our boundaries over the years, and DH cannot seem to tell her "no", he always gives explanations. She doesnt get it.

- Toxic Troll has asked to borrow truck to haul furniture.
- She has asked DH to measur her grungy apartment for her for furnishing.
- She has texted sexual suggestive comments.
- Just a few months ago, Toxic Troll ran out of gas a few blocks from her apartment, asked DH to come resue her, on his way to work, and then freaking waited ALL day for him to come rescue her after he got home from work. I went through the roof on that one.

You need to set some boundaries for your DH, and continually enforce them.

Not exactly, but when my husband has to be around his ex or deal with her in any way, he becomes agitated, anxious and almost scared.

I remember asking why he wasn't looking forward to his only child's wedding a few years back. He said he can't enjoy anything involving his ex because her unpredictable behavior just shakes him to pieces and brings back scenes from their marriage, which was pretty ugly because of the ex's Borderline Personality.

They had an abusive relationship -- she was verbally and physically abusive and a raging, destructive force to her kid, her husband, her bosses, everyone in contact with her, which I only say because I saw it in action and she directed at me a few times. I was terrified!

If your guy had a rocky relationship with his ex, maybe one that shook him more than you realize because she's not altogether stable, maybe what seems like his rudeness to you or obsession for her is really anxiety. He might be trying to keep her in check so she doesn't flip and is ignoring you in the process because he knows you aren't off your rocker and won't make a scene.

Maybe he was difficult the day before the graduation because he suspected she'd show up and make a scene -- just as she did...in spite of a judge's order that she not do so...which is pretty disturbing when you put it that way. Or maybe seeing her is (still) just that awful for him because the relationship left him too raw or ended too recently.

If I'm way off, disregard this. But try to figure out for sure if what you're seeing is his way of coping with an explosive or impulsive ex or maybe his own emotional fallout from that rocky relationship. I was  shocked when I realized how emotionally damaged my husband was from that first marriage -- maybe your guy is too.