I think. YABU.
But then YANBU for wanting him to savour the moment as regards your children.
Realistically they will make an offer. If it's better than what he's on now then he'd be a muppet to start demanding better terms.
A degree is neither here nor there in many ways. It can be very important in some institutions, a pre-requisite of employment even, but there are always those who haven't got one who will impress enough.
I wouldn't even argue about this and CERTAINLY do not tell him to 'set his goals lower'!!! Jesus, I'd be utterly wrecked if anyone actually said that to me, least of all the one person who professes to love me most!
You need to tell him to go for it, but be realistic. Encourage him to succeed (without sacrificing your own dreams of course) not to be arrogant, wait for the offer, reply with either an acceptance OR a very well thought out and researched reason why he's worth more, then negotiate.
Never set your sights low.
Also if a degree is needed to move up the ladder, you can study for a degree out of work, burn the midnight oil... one of my colleagues has just gained her PhD. It wasn't easy. They had to timetable every single minute of their life, she worked full time AND has children AND no partner.
Work/Life balance IS important, but it's quality not quantity that counts. If your DH makes every single second of family time quality time, your children will not miss out (Unfortunately he may become the hero whereas you'll be 'boring' - meh, that's life sometimes, my children will appreciate me most when they have children!!)you need to do something for you.
So I say YABU. You need to set YOUR sights HIGHER. Good luck :) (Nothing wrong with being afraid).