I've read the last ten pages of your sitch Idont . . .be careful man, and do a little thinking for yourself. I'm not even gonna try to step on anyones toes here.
One thing I will say though is I wouldn't spend so much time rehearsing 'your voice' and what you're gonna say, as much as I would recommend getting more stoic and zenlike. Imagine yourself not being rattled by ANYTHING . . . Imagine yourself being like Spock on Star Trek: Nothing rattles you. I'm serious too. It's good to give some thought to what you might say, but when you try to rehearse and think about everything you want to say, and how you'll say it, all it takes is one unexpected statement from your wife. Then Bang! It throws everything out of kilter, ya forget what you wanted to say, you realize you missed something you should have said two minutes before but forgot to, then you try to work it in, it sounds contrived to you, you see she's looking at you weird, she says something else you weren't expecting, and next thing ya know, you're frustrated, you get emotional, and ya just want to rewind the clock but ya can't. "Been there done that" with the rehearsal thing. Getting the mind to "Be Cool" naturally is the way to go there.
It's the mindset ya gotta work on, not the words or the voice. Once you get the mindset right, the 'voice' takes care of itself and if you missed something, your stoic and level mindset reminds you you can work it in some other time. Imagine a worst case scenario, like you walking in and catching "them" red-handed "together" Imagine yourself looking down and instead of freaking, Just scowl a little and you begin "Now ya see? This is the crap I'm talkin about. This is gonna stop, or you can just pack your stuff and get out now." I'm serious. Send this clown home for good, or pack up your stuff."
Okay . . .I'm not saying I could be that stoic and level-headed. I've BEEN in that pretty much that situation as my first marriage ended, and even with the benefit of hindsight . . .yea, I'd probably kill the bastard while she watched. But I can still visualize myself being cool but assertive under that situation so pretty much anything she simply "says" is gonna be tame by comparison. I'm not saying visualize "the deed", I'm saying visualize yourself laying down the law stoicly, calmly but assertively to her. Spare yourself the details there.
All this stuff is more like a basketball game than a hockey game anyway. Know this, and it'll help you keep your cool under fire. In a Hockey Game, two lapses in your defense can cost you the entire game. Luckily Hockey has little relevance to a marriage.
A basketball game is a series of shots and scores. Sometimes ya hit, sometimes ya miss. What do ya do? You just inbound the ball and keep playing, that's what ya do. If you stand around denigrating yourself about that missed shot or being out of position that allowed your assignment to hit 'the three' you just allow another chance for the opponent to score again. Of course even if ya do THAT . . . just get your head back in the game, because you can still win.
But mindset is important. Athletes use visualization as we do in martial arts. A boxer who "hopes" he'll win is a boxer who is about to get his tail kicked. Further, ya can't just freak out if you get tagged with a solid right. Gotta keep your head, be cool. That doesn't happen by accident. Boxers spend a lot of time, the goods ones anyway, getting their mindset right so they can think and function under pressure. Think like that. You have to come across as cool under pressure. And while you could rehearse and "fake" it" Admittedly I have 'faked' it in the past few weeks, but generally I maintain enough control "real control" over my thoughts and emotions that, for example, my wife wanted to make love a few nights ago for the first time in awhile. As we got started, she said "Don't read too much into this" In my first marriage ending, that "YES! She wants to have SEX! She doesn't want to leave! Emotion probably would have reared it's head, only to be emotionally flushed down the toilet with that "Don't read too much into this" statement.
Luckily . . .I was already telling myself not to read too much into it (Thanks Michelle) And I cooly . .and genuinely, replied "I'm not" rather matter-of-factly.
I have had to make a conscious effort to visualize myself as genuinely stoic, level-headed and cool throughout. And you need to "be in that place" before going into it, to the point you don't even have to think about remaining there once the talk starts and at least so far, I haven't simped out, though, I've 180'd a few things. And so far, I don't feel any desire to point out how great I am for making these changes. Haven't said a thing about it, I'm just doing it. Not pointing out every time her daughter disses her. Making my job search efforts more transparent, since that clearly is an issue, and I kinda kept that stuff to myself. To me, I admit it just seems a bit 'weird' to make job calls in front of her, fill out applications and customize resumes with her there, etc. I tended to wait until I was by myself to do these thing. But it truly does seem to make her feel better. I suppose she can actually see me doing something. That was "counter intuitive" to me, because dang . . .It seems kinda rude to me to do that stuff in front of folks, my assumption was that stuff is boring to her . . . but it seems to give her reassurance.
Again, keep in mind I'm just posting my thoughts, and some folks'll hate that. Take if or leave it I suppose. I'm no expert, don't pretend to be, and I am not out of the woods yet myself, but good luck!
Life may be short, but . . . well . . . it actually IS short, now that I think about it . . . . particularly when compared to planetary formation and stuff.