all this time that he saw me as a bill
While in fact you have been contributing in a very major way, to the family. Have you worked out, just for your own satisfaction, how much he would have spent in childcare and housekeeping never mind the children in the first place? Not just so easy.... I would really encourage you to get a copy of The Lady, have a look at what a household staff would have cost him.
Not to counter his view (as you see it) but to boost your own self confidence, which sounds as if it really is at a low ebb. As a stranger reading your story I have no idea of the dynamics of your relationship, but I do know that the place to start is with how you feel about yourself. Again as a stranger, I read about your accomplishments, three lovely children, two degrees and a masters and yet what comes across is how little you seem to value these.
Your DH has at least been v v tactless, which isn't great, but instead of noticing that he has been horrible, and needs a wake up call, you seem to be internalising what might be his view of your low contribution (or might be an isolated, unwise, unkind comment).
Going back for a moment to your pay cut all those years ago, how do you feel about that. It was a (another) horrible thing to happen to you and it is no surprise that it might have seriously knocked your confidence in yourself, as an external party's view of your worth. Did you internalise that one to, do you at some level maybe got the idea that you were worth less, rather than really unfair, really bad experience in your life
Before you make any serious decisions about your life from here, please do some work on your own self esteem. What do you want, what do you need or yourself, what do you offer your DC, DH and the world. Knowing the questions can be helpful in order to start looking for answers from within yourself, rather than accepting the opinions of other people. Other people have less at state than you do, and may make careless remarks which, if taken as 'the truth', would be very hurtful.
Then have a look at your life and decide what you want, for your DC and yourself, from a position of strength in your own self esteem. You might find that DH just needs a nudge to make the sort of relationship you really want. Or you may start to make wider plans.
I am sure that i have seen ads on Facebook to support women return8ing to work after a career break. They will put all this much bette than I possibly can, and may be just the hand u you need now. All the very best...