S.W.
No job is stable. I've worked in Outplacement for four years and met with hundreds of people who have been laid off from jobs of all kinds. Many of these people would have told you their jobs were "stable" and they were "critical" to the company. No, they weren't.
I would not quit a job unless I had a 9-12 month emergency fund. The average job search is taking 7-9 months and I know people who have been out of work for two years despite continuous job searching.
A retirement fund for both of you needs to come before a college fund. There are options for college money but not for retirement. Also, if you are out of work, you are not adding to your Social Security amount that you'll qualify for.
I would never chose to "scrape by". I don't feel that is fair to my family. There are a lot of unknowns coming in life (financial, medical, career, etc.), and money is one way to prepare for those unknowns and to provide more options and opportunities for my children.
If you are depressed in your job, maybe you need to look for a different job.