In all the other posts about "should I stay with my spouse for the kids", everyone always says no, don't force a broken relationship "for the kids" because then the kids just grow up seeing a broken relationship and thinking it's normal.

This is completely broken and OP should absolutely divorce if he wants to. He gets to make that choice if he wants. If he doesn't want to and instead wants to work through it with her then that's also fine of course.

But don't try to act like "staying together for the kids" is suddenly somehow obligated in this particular situation or the better choice when any adult from a broken home will tell you they'd rather have had parents who were apart and happy than together and resentful.