Are you really prepared to do that if she continues the A at this point?
Think really hard about that.
Adam, you keep using the word boundary, but you're talking about an ultimatum. To paraphrase that old saying, you only point a gun at something you're willing to kill.
The way you describe it, you're ready to go to her and say, "You have two choices: stay in this marriage, or GTFO." Which do you think she'll pick? How will you feel after she picks it? How will you feel a week later?
Go back to DR. Re-read the section on LRT. Then take a closer look at "after LRT" starting on p. 218. Both of those are better options than an ultimatum, and yet you don't need either of them.
Yet.
H: 35 W: 33 M: 11 T: 13
4/10/18: I discovered A and confronted ("BD1") 6/23/18: I moved out 8/31/18: MC ends ("BD2")