I say quit :) In a heartbeat! So much money, wife's support of the decision, your emotional state, yep.
If I took the risk and quit, it could be two years of feeling like a deadbeat, being unable to get a business going, and disappointment.
Even if you don't create a successful business within two years -and most people don't- that wouldn't mean you'd been a deadbeat. It would mean you spent two years learning, practicing, testing the waters, finding out (more of) what you're good at and what your weaknesses are (and where you would, thus, need to hire support). Those are all excellent explorations/foundations for future business success.
I would propose the reframe is not about getting happy in your job if it's no longer a fit, but rather in regards to what becoming an entrepreneur is and involves. It's not always instant or early cash flow. The potential benefits are not only financial, but those of joy, learning, growing, and subsequently landing somewhere happier than you were in the Job-Job you left.
This said, I would also propose that you would have some responsibilities such as:
-legitimately working full-time on entrepreneurship OR filling in some of the gap hours cooking and cleaning for your family
-being super responsible with your guys' family income, to counter some of the effects of stepping out of a Job-Job
-supporting your wife's freedom to spend the higher amounts she feels the need to (i.e., being mindful not to reign her stated needs in just because you opted out of a Job)
-maintaining some work-life balance, i.e., making sure you are about as available to your wife and child as you are currently (i.e., don't drown yourself in entrepreneurship at the risk of the relationships); this can feel tricky in entrepreneurship but it's important
-testing the waters (your skills, your endurance, etc) with a low-cost start-up rather than a high-cost one (there are books on the former)
-being willing to call it if something's not working, and move on to another project OR another Job-Job
That kind of thing. So, not just throwing caution to the wind and experimenting mindlessly, for example. (I don't think you would do that, lol.)
I always hope that people in a position to be free will take it! Dreams, happiness, self-actualization, contributions not necessarily attached to financial rewards, etc.