Sorry for long thread but there is context and don't want to drip feed.
DH is a teacher and has recently had a "tap" to apply for HOD job at his school for next September.
I am the breadwinner (earning c.5x DH's salary) but there are elements of his job which contribute massively in financial and non-financial ways (huge discount on school fees, DH does all childcare during school holidays).
I am pregnant with DC3, due in the spring and have made big sacrifices for him to pursue his teaching career. I went back to work after 3 months with DC1, and 6 weeks after DC2 because he was doing a degree and teacher training so I needed to earn. I have stayed in my current job longer than I would otherwise have done because the flexibility is amazing, but I have to do a night away a week from the kids and a long commute either end. Whenever the kids are sick during term time, it is me who juggles as his job is less flexible.
We are finally settling into a routine but I am stretched/often struggling. I do school drop off and pick up 2x a week on my WFH days (plus on my day off - I work 80%), spend a couple of hours with the kids then finish my work day once DH is home from school. It's working, but it's not easy.
The HOD job would involve him moving from 80% to full time as well as significantly more admin to do before/after school. Which ultimately would involve us needing a nanny for an extra day (which would more than eat up the pay bump for him) and add significantly more strain on me when I already feel like I'm just getting by.
He also wouldn't be able to take shared parental leave as we had planned for Christmas term next year. I've said I think we should just focus on stability during the early years and spending as much time with the kids as possible, and that the HOD is likely to come up again at some point. Once new baby is at pre-school, I am likely to want to look at different job options which would be made a lot easier if DH just stayed where he was for a few years. He's saying that we both worked hard and sacrificed a lot for his career and that he now wants to climb the ladder and start taking some of the financial load off of me. AIBU?