Appreciate your perspective

Hello, I am a 45F looking for guidance and insight from this group. Here is our financial situation:
Combined income: $400-$500k per year
Assets between brokerage and 401k: $3.6M
529: $150k
Cash: $140k
Mortgage: $700k remaining at 3% (house worth around $2M)
No other debt

We live in MCOL place, two kids in public school ages 12 and 14.

My husband wants to work for another 5 years, but I desperately want to quit my high stress tech job and start my own consulting company. It feels irresponsible as I’ve been making good money for a long time and I have all kinds of fears that I won’t be able to get it off the ground, and as it stands, my husbands salary doesn’t cover our monthly spending.

I’ve been tracking our spending on Monarch the past 3 months and we spend about $12k a month.

Would love to hear all your perspectives.
TIA!