I am so sorry to hear how you are feeling and what a difficult time you have been going through.
I can see that you don't feel any of the advice to leave or to let her/ask her to leave is right.
You have to do what feels right and reasonable to you. Only you can really know and understand what is in your heart.
So just a few thoughts, in a way holding up a mirror and reflecting back to you what I see. If any of it is useful, great. But I am in no way trying to tell you what to do.
Firstly, it doesn't seem surprising to me that counselling has not helped you. Actually, at this particular stage, perhaps you are not the one who needs it.
Putting everything else to one side for a moment, what you have said paints a picture of a woman who is very unwell.
It sounds as though there is something very wrong, and as if she needs a) to recognise this and b) to get some help. The text messages, her saying they were 'nothing', and you being able to entertain the possibility that she is actually making it up . . . this is not a healthy situation for her, let alone you.
You have said that you love and care about her. Also that you put your child first. For the sake of all three of you, my feeling is that the focus must be to somehow get her some help.
I would reiterate, as I think you are aware, there is nothing wrong with you other than being worn out and ground down. At the moment you seem to be saying that your heart has no protection left - that the things she does are excruciatingly painful. You have an open wound and she is pouring salt onto it. Somehow, she must be stopped from doing this. It is destructive and frightening behaviour.
All this debate I have read about 'being a man' etc etc seems to be just a red herring to me. This is about the present - about how you deal with the present and move forward into the future. You are a caring, straightforward man who is very bruised and wounded. You are yourself, and there is no need for you to have to justify that. If there is anything a bit skewed, it is probably (and naturally) your perception of 'what is normal'. When we live with a bizarre situation day in and day out, we stop identifying odd behaviour as 'odd'. Incrementally, strange behaviour gets accepted as normal.
She is deliberately causing you pain. Why?
Sometimes people cause pain to distract them from dealing with their own pain.
What if she began to cause your child emotional pain?
This atmosphere of hurt and destruction doesn't sound healthy for any of you.
Can you think of anything you could say to her or write down for her that might give her an insight into how she is behaving?
Perhaps, like an alcoholic, the first step has to be for her to recognise the problem?
Sometimes I find it helpful to write down the bare facts. Never mind what the intention was, never mind what the various people involved meant or thought or felt.
What was SAID?
What was DONE?
What happened in actual FACT?
Might this make her recognise that some of her behaviour has been unreasonable?
What do you want to feel like in the future? Forget the living situation for a moment. How do you want to feel?
Right now, what would need to change to achieve that feeling?
I hope that I haven't come across as lecturing, that's not what I mean to do. It's just a stream of consciousness reaction. This situation is out of the ordinary, and you are going to need extraordinary strength and extraordinary support to get through it and come out happy one day in the future.
I wish you all strength, good fortune and happiness for the future.