Joet,
Not much in a way of suggestions but wanted to say that I understand all too well and wish you luck. I decided to delurk from reading the blog and the forums to admit that we are roughly in the same situation (similar income, net worth and level of expenses albeit somewhat differently distributed), so I understand where you are coming from. While my "lofty" goal is to get our spending closer to 6.5K/month, including 2+k in childcare, every month that is below past 12-month average feels like another baby step in the right direction.
And for what it's worth, I am coming from the same position as your spouse - I saw no reason to keep an eye on spending as long as all retirement account contributions have been maxed out, some amount put aside in taxable and we carried no debt. So we didn't outspend our incomes or lived above the means but we have been pretty wasteful. This has changed as my love for my job has slowly turned into a burnout (a startup I worked for was bought by a megacorp a few years back and slowly turned into a soul sucking circus). MMM opened my eyes to a possibility of FI/RE and while I am unlikely to ever get off the Antimustachian Wall of Shame and Comedy due to high levels of un-optimized spending, I stopped plugging the holes of general life dissatisfaction with random purchases and became a lot more focused on saving and reducing expenses in order to hit both targets of saving 2m in 6-7 years and dialing down the expenses to 6.5K/month (or 4.5K once the childcare is no longer an expense).
I never thought of myself as profligate (ha!), but have become all too firmly attached to bedpan and caterer lifestyle of throwing money at every inconvenience. Trying to ween myself now. All this to say that it's possible that your spouse will see the light and I wouldn't give up on it. I would have been pretty averse to money saving "talks" if my hubby initiated them (because I worked my tail off, brought in my share and felt entitled to spend it as I saw fit as long as there were no "obvious" issues with spending above the means or not funding 401ks/Roths.). Now that I have this burning desire to gain financial independence, I am a lot more receptive but the steps are still baby sized. Hedonic adoptation is a bitch...
FWIW, we have ours/his/hers money streams and earn roughly the same, so generally most money arguments have been avoided by one of us sponsoring our own spending that is not related to advancing as a family. This has been working pretty well for 13.5 years from the marital agreement perspective but it also leads to lack of analyzing whether the spending is meaningful in the big picture.
