Please don’t shoot the messenger!
Like I said - you need to speak to a solicitor with recent experience of your situation (which shouldn’t be hard as it’s not uncommon!)
Does choosing to work part time count for nothing? Well, in a way - yes. It was a choice you made. One which you may now regret. But remember you had that additional time with your children, which you may think was worth it. I’m a divorced parent, I’ve turned down promotions because I prefer not to be away from my child more - sometimes, it’s worth it. So keep that in mind if you feel bitter.
Sounds like you’re of an age where your mortgage is paid off, and you’re old enough to have perhaps gained heavily from house price increases. Earning 4x your salary, perhaps your husband’s pension is good too. So 50% of these and other marital assets could be very good.
You argue you haven’t retrained, but my point is that a diploma, degree and professional qualification, and 8 years back working full time puts you in a position where I would think you can’t ask for a transitional payment (spousal maintenance) to help you back into the workplace. As you might if you were a SAHM who hadn’t worked in 20 years.
Yes, you supported him to earn more - and you gain from that now, if you take 50% of all assets. Those assets are higher because he is a higher earner.
Speak to a solicitor.