My issue now, as petty as it sounds, is I can’t stop feeling this hatred towards him for lying, and getting away with lying. He’s become the perfect boyfriend, to show everyone that he couldn’t possibly be a liar, and that I am the deranged one. I’m not as shocked by his behaviour as I am about how disgusted I am. I want to go back to a place where his lies- or any of his actions- don’t affect me.

I think your anger/hatred/disgust is justified in this case, as he has definitely done things to deserve that reaction. I’ve learned, though, that it helps to get rid of anger by looking at all of the possible sources.  For instance, I was really mad at my ex for a long time because of the things he did after he ended our relationship, and, like you, I didn’t want to waste the energy on being mad at him and couldn’t figure out why I couldn’t just let it go. So I started digging deeper for other reasons why I may be so angry and realized I was actually more angry with myself. Sometimes we can get mad at ourselves without realizing it when someone makes us feel like a fool or drags us into drama that we don’t want to be involved in, and our anger for the other person can sort of hide this anger we have for ourselves, so if you dig deeper and realize you’re angry with yourself for your part in getting into the drama… and we can even be mad at ourselves for irrational things we couldn’t possibly have known the result of beforehand, like being mad at yourself for ever dating him in the first place… if you figure out exactly what you’re angry about when it comes to your part in things and you can forgive yourself, especially if there is a lesson there you can learn so you don’t find yourself in that situation again if possible… I’ve found that lessens quite a bit of the anger.

The rest of the anger you feel for him will lessen over time. You just have to sort of feel it when it comes and let it pass on through. As time passes, thinking of it will upset you less and less.

As for him and his girlfriend, I would do your best to just detach from them and their situation completely. You did your part in telling her what he did, and I think it was a good thing for you to tell her because she deserved to know, especially since it had been an ongoing thing of him saying he missed you while he was with her. She is the one who then chose to eventually disregard when you said. That will likely blow up in her face later on, and that will be her fault and something she’ll need to come to terms with then. He may be acting perfect now, but he is very clearly not perfect, so he will only be able to keep up the act for so long. Please rest assured of that.

So in order to get back to that place where his lies and actions don’t affect you, cut him (and her) out of your life completely, don’t let them back in, and then just give yourself time to heal, be patient with your feelings, and the anger will eventually dissipate.