Hung out with some friends yesterday for a tabletop game and I found myself feeling a lot better.
Good. You're human and you should now recognize your internal need for camaraderie and social interaction. Do more of that to feel more of that. This won't replace the relationship you had with her, but it will help remind you that you necessarily gave up some of this for your relationship with her, you need your friends now, and it's a good time to strengthen those bonds.
basically right at the end I made myself feel like shit again
Yeah, that sucks. You're human and without external stimulation and during moments when you don't have to act, you reflect on the past and try to come to grips with it and re-evaluate your "scripts" you follow under certain situations. Sometimes you can improve yourself, other times you just end up beating yourself up.
I felt slightly better before leaving, but she was still in 3 of my dreams.
Good. Your sleeping mind is still coming to grips with the relationship changes. Don't read anything into these dreams.
Thing is, I was feeling anxious about feeling like I need to do something (spoiler alert: I shouldn't do anything) but now I'm anxious over whether I want to do something or not. Should I really make an effort to let go, or should I pursue her? That kind of stuff.
As long as you continue to believe that there's a chance, no matter how slim, of getting back together, you will always have these feelings and thoughts.
If you don't like this ride, then get off it. Close the door to those thoughts. Tell your friend(s) you don't want to hear about her current activities. When you do meet her, say hi, but don't try to chat or flirt - acknowledge and move on. In all your actions and interactions assume that the two of you will never be together again and act accordingly.
If, however, you like feeling this way, continue to hold hope in your heart, ask your friends about her, and flirt whenever you see her.
I don't think I'd enjoy it, but who am I to tell you which way to go?
Regardless, everything you're experiencing is expected and normal. The only thing you have power over is what you'll do with those things. You can learn from them, move forward and grow, or you can use them to beat yourself up, dwell on the past, and hold onto the idea that maybe you can go back to what you had before. Spoiler alert - you can never go back, even if you do start dating them again it will never be the same.
So I always advise moving forward and letting the past stay in the past. If it's going to happen again in the future, it'll happen whether you hold onto it or not. My experience, though, is that if you let it go, and you grow from it, then whatever relationship you do enter into in the future will be surprisingly better than what you had in the past. So let it go, grow, and look forward to future relationships. Focus on what you want to be for your future partner and become that person, rather than focusing on what you got out of your previous relationship(s) that you now miss.