Cleo, Sugarbooger, other jealous lovers:
We all feel jealousy sometimes. Poly people are not Nietzschean Supermen, miraculously grown beyond all human emotion. I recommend that instead of letting jealousy beat you into misery, that you take it as an opportunity for introspection and communication.
Jealousy doesn't mean that you're unfit for poly; it means that you fear something. Ask yourself seriously what that fear is. Why does the idea of them boning for 2.5 hours upset you? Why does his staring into space make you insecure? Is it because you feel like he might be better than you in bed, that she'll steal him away? That you're sexually inadequate? See if you can have a real conversation with your amygdala about this. Then have a real conversation with your lover.
"I feel inadequate when I imagine you two going at it. Until I've gotten used to the idea, I need your support. I need you to tell me you like boning me too and that it's not a contest. I need you to tell me that once and hour our so.
" Or whatever.
And then, once you've done that, you can train some of that jealousy away. Usually jealousy makes you instinctively want to do exactly the worst thing for the relationships. So train yourself that when you feel jealousy, you do the exact opposite of what it's telling you to do. When it tells you to imagine the other two boning, don't do that, and have a jack-off session starring Angelina Jolie. If you're compelled to ask him who he's thinking about, don't do that, and tell him who you're thinking about instead.
And, I think, most importantly, get to know your metamours. Go to dinner and a movie. have girl talk. Go to the bars. Give gifts. Knowing and loving the metamour brings all three of you together.