I find it strange, this idea that a SAHM should feel grateful to her DH for giving her the opportunity to be at home with the DC while he takes on all the stress of being the sole earner.
They are his DC too, not just hers and lots of dads prefer that their children are looked after by the mother rather than paid childcare. I know that my DH feels less stressed when he has to go away for work or do long hours, because he knows the children are here with me, not with a CM.
His life runs more smoothly because I am here and my being at home has enabled him to focus on his career and increase his earning potential. I don't think our lives would be better if we both worked (in lower level jobs) to bring in the income we have now. My DH likes his career.
So, while I appreciate how hard he works to provide for us, he also appreciates that what I do helps him to achieve that. I don't think one of us needs to be more appreciative than the other, because we are both doing what we want.
I think the OPs husband should appreciate her contribution to their shared life and acknowledge that in caring for their children, her career options have been reduced.
I would be quite worried if my DH thought I should get some menial job during school hours, because he couldn't stand the thought of me having some time to myself during the day. If the OPs DH wants her to work then he needs to understand that his days of getting home to a house where he doesn't need to do very much in the way of childcare/housework/cooking are over!
If he's going to happily give her the time to retrain and find a proper career, then support her by doing 50% of the house/child care then fair enough. If not then I consider him to be in no position to be making demands.