Hi Lily,
I have been following your thread since the start. First of all, I just want to say how much I admire you, I think you are doing exactly the right thing and I think you are doing just great. I'm on the sidelines, cheering you on. You may feel like sit, but he doesn't know that. Good.
In terms of NC - I would be doing exactly the same. I would not want to give a cheating ex the satisfaction of knowing how I felt either, no matter how devastated I felt. In fact I have done this myself, and would do so again. There is a great deal of power in silence. Paradoxically, your silence says far more to him than a thousand words ever will.
And it will raise doubts in his mind. I suspect that your silence will at some point cause him to question his decision. If not now, then further down the line. I also believe there is a chance he may try to come back at some point in the future.
When you are out of this at the other side - and you will be - you will look back and be glad that you maintained your dignity.
Don't be too hard on yourself. You are grieving, and grief is not a linear process. It's like the tides coming in and out. It ebbs and flows.
It's probably not much of a comfort to know that you are going through a period of intense personal growth, which ultimately will make you a stronger, more compassionate and more insightful person, but which unfortunately is totally sht while you're going through it.
It is okay to feel sad, shocked, angry, confused, sentimental about the past, and all of the other contradictory feelings that follow. Don't fight try to fight them. Accept them.
They say that "To feel is to heal". Tears wash out stress hormones and other toxins associated with stress. They're literally a physical and emotional de-tox.
Right now you're wading through the fog of confusion, having had the rug pulled from under your feet. But a few years from now, you'll look back and see the situation much more clearly, and view your ex in a much less romantic light.
FWIW, his ridiculous and inappropriate behaviour posting on social media says far more about him than it says about you.
Keep on keeping on, Lily. I'm cheering you on from the sidelines.