Yes, go dark and start packing stuff, prepare your family to embark on a new chapter.
If you absolutely must reply, and I still suggest not, try this:
"If you are not lying or justifying, then we can't have a real marriage..that is the sad conclusion that you forced me to come to.
I'm not giving up, I'm just giving you the opportunity to decide what it is you want and need. The current state of this marriage is unhealthy and unfair (to put it mildly) for me.
You say that the kids and I are your world, that you want to be home with us. I see someone that decided, in the midst of this turmoil, to vacate for 10 days to be free of the 'negativity'. Negativity, I might add, primarily caused by your decisions and actions.
Yes, the trip was planned, but what exactly are the priorities right now?
You want help? I am helping. Until your decision is both clearly articulated and actively pursued, I will continue to help by protecting against further marital sabotage.
Good luck!"
Then, what I really think needs to happen is to start backing your resolve with clear action that you mean business! She needs to see that; clear-cut action is key.
I know I sound harsh and obviously, not being embroiled in the emotion of it all, it is certainly easier said than done, but those responses from her are pretty loud signals that she wants a rug-sweeping pass on this and then she can continue on with life as she knows it...with a marriage of convenience, no respect for her mate and secure in the knowledge that this sort of thing has no real consequence for her.
And you're stuck in misery and always wondering if or when you'll uncover another A.
She doesn't 'feel' it yet; give her THAT FEELING and I believe there is a chance the M can survive, if she chooses so. She won't choose it if things remain this way. I know you're afraid 'harsh' will turn her away, but 'nice' will DEFINITELY turn her off the M.
What 'harsh' will do, is if she has it in her heart that you and the family ARE INDEED IMPORTANT, she will choke down the stubborn/unwillingness, then start WORKING TO PROVE that's what she wants. And you really don't want it any other way than by a true, desperate effort on her part.
You explained that she has the option to choose M and if that is the case, there is some reasonable criteria to go along with it. She merely has to choose and start walking the walk. I'm fairly certain she 'knows' what you want her to do, but she balks/negotiates in hopes you'll just 'let' her back in.
Start moving on and she'll more actively demonstrate her true desires.