Op, I mean this gently, are you lonely or bored? Just you seem to be making this all about you, even the “I fucking hate him” comment, staying up late, writing poems about him, starting threads, now wanting to cry as people rightly pointed out you can’t do that,
you even wanted to do it and behind your daughters back, secretly, but the only thing stopping you was if your daughter found out, so you knew how hurt she’d be, how angry , but you really wanted to do it anyway, putting your needs first, in her breakup, like it was yours. You even wrote it would make you feel better and how you wanted revenge. Can you understand why that’s a little worrying?
I would focus on what’s the root cause behind this, is there something going on or lacking in your life maybe?
This is something I’d personally self examine on, and then try to resolve what’s causing it. Getting out more maybe, increasing your social circle, changing job, volunteering, taking up a hobby, because if you’re living so vicariously through your child that you actually seriously consider getting involved in her relationships behind her back, then you need to fix that.
good luck, I’m sure with some self examination and effort you can make a big difference to your own happiness.