Stepdaughter

I told Stepdaughter on Facebook that Ex has a new girlfriend, and that I was sad about it, and had tried to make our relationship work, but he had chosen to date Bitch instead.
I feel kind of bad about that, but you know, she's my friend too after all these years, not just Ex's stepdaughter! She has a right to know. I know he would want to protect her and not tell her til he has to, but you know, she's an adult now, and I didn't tell her all the bullshit, just the fact that he has a new bitch in his life.  
She is living abroad, otherwise I would have called her or something. Haven't had a response yet. She doesn't check in too often.
That's nothing, you should see the email I had thought about writing his parents and brother!! I think too much of them to let them know, otherwise I would have dropped him right in the shit. He is favourite middle son, and the sun shines out of his ass, according to them.

Don't think I wasn't tempted. But I didn't. Of course. 

How do you be a nice person, remain ethical, keep away from the urge to massive unrelenting revenge? I have been having all kinds of thoughts, like wishing I had a way to sneak in some sexy underwear into his room for her to find, or leaving dead fish in the curtain pole, or rubbing hot chilis on his underwear, fake phone calls from the STD clinic, etc.. All the classic stuff of urban legend, an inspiration to me at the moment I'm afraid. I have the urge to wreak utter havoc in their lives.

Honestly, what is stopping me?  Probably not ethics, or niceness, probably just the fear of karma, or of being found out, and burning bridges in case I ruin any chance we ever have at getting back together again.  I would love to say I'm bigger than all that, but I'm not sure that's true. If I thought I could get away with it, I might well do something nasty and vengeful and mean. 

I need to stay with that feeling of pure Love that I felt for him this morning.

There could be more poison being spewed here for the next while, so that it doesn't leak into my actual life.  I can't afford to let it.