Terle Glens advice here is sage. I'm afraid what you are describing is what happened to me (minus the kids) I understand the descriptions you are using here. This is awful for you. Please talk to us to help you to come to terms with your feelings about this, if you can seperate your anger here you may be able to see a clearer way forward. However you feel, try not to make any big decisionss tonight, split up/ don't split up or whatever, you are too emotional to be rational about this. Try to keep all options open, don't close any doors. You love her, you can see she is in the grips of something, you know there is a real reason for her not to be feeling, but you also have a right to be upset, angry, VERY frustrated, and devastated about what seems to be happening. Things may not be as they seem.
Try when you are talking to her to ask her open questions; 'what makes you say that..' when you are talking about how you feel talk in 'I statements' I feel this way...' Don't get into a you made this, you made me feel, deffensive type of argumemt. DON'T have a drink whilst you are talking/arguing, try to remain calm and keep the situation calm. Take yourself out of yourself and see it as a challenge - like you're been told 'I bet you can't keep calm in this situation' candid camera type of thing - If you are calm, it will have a calming affect on her, even if it doesn't appear so. Aim for explanations, but remember there may be none.
Saying you would be better off without me, you could be finding some one else, is very likely a cry for help. The possible decode for that is 'I am such a mess and such a failure and you have seen me so at my worst I am embarrassed and can't imagine how you could still want me please explain to me how". Don't stop telling her how.
If your wife comes on here and you want me to delete this post after you have read it I will. And if I'm not around when you req then I give my permissino for any mod/admin to delete it on my behalf.
I am thinking of you. Take some breathers during your conversations but always come back to it.
Let you frustraton and anger out HERE, NOT to your wife, calmly and as eloquantly as you can tell her how you feel but don't lose it. lose it here.
&*(