Find some pretext to get yourself laid off. Today. That way it won't look like your fault...
...Just kidding! I don't ever actually recommend deception; in the long run honesty is much less work.
Seriously, you and DW need to become MORE honest with each other because apparently neither one fully comprehends where the other is coming from. DW "smiling" when you bring up the subject of backing off suggests she doesn't believe you mean it; and you seeming mystified by her reluctance indicates she hasn't offered a compelling case for it - or at least if she has, you don't know what it is.
Maybe she hasn't fully grasped the solidity of your finances. Maybe she is secretly thinking about stepping up to a plusher lifestyle. Maybe she fears that retiring too early would set an example of a poor work ethic to the nestlings. Maybe the concept of early retirement is simply too foreign to register in her brain (my late MIL would have had this difficulty). Who knows what her reasons are? Apparently, not you!
So you two lovebirds definitely need to talk this through, and then talk it through again, and again, and a hundred times until you reach mutual understanding. You may find that once you accurately see why she isn't on board, you'll think she's right!
I'll have to disagree with some of the other responders who seem a bit trigger-happy with proposing divorce. No doubt they have their own valid experiences influencing their viewpoint, but it isn't clear how adding an extra heartache on top of the employment-derived one is going to be helpful. And in any case, it's WAY premature to exercise the nuclear option. Five bad months at w*rk? That's a long time to sit on a stove, but that's not even a OMY situation. Hardly a case for sundering a marriage. Better to just get a different j*b that doesn't $uck.
Anyhow, yours is an interesting story. I can't wait to read the next installment! May you live long and prosper.