Chastity and orgasm denial discussion

So my Mistress (my wife) and her close friend really like each other. Her friend is gay, and this weekend I watched them kiss and dance at a massive pool party while I was locked up the entire time. I told her friend about our chastity setup. She seemed surprised but totally cool with it. We’ve got an understanding that they can make out freely when I’m not around, but if things go further, I need to be included. It’s clear she only wants my Mistress, though we haven’t figured out yet whether I can pleasure her directly. The only sexual relief I get is from my Mistress myself. While kissing is fine for me, I wonder if watching them have sex would be too much to bear. Our marriage and their friendship are the most important things here, and everyone’s feelings take top priority.