@FabbyChix did you miss the bit where the OP has made serious career sacrifices for the children's care, while her ex has made none, and that her earnings are massively lower than his on that basis? Honestly, some women's determination to belittle the unpaid sacrifices their fellows make for their children is deeply depressing.
OP, you need proper legal advice. Nobody here can advise you - family law is case specific and every family's situation turns on its own facts.
If you can sort it between the two of you, that's always better. If you have a flexible job that facilitates school runs, and you only have the kids half the time, then I'd focus less on what money he can offer, and more on the increased space that gives you to focus on rebuilding your career prospects. Even if you did get CM and SM, he could lose his job tomorrow and you'd get nothing. Far better to look at whether only needing to cover childcare half the year would allow you to really make a career difference.
Might also be worth asking him what his plans are for childcare, and what he will do on his days when they're ill - and make it plain that if he wants 50/50 then that means he will have to step up, and do all the school plays, concerts, parents evenings, dentists, doctors, parties and sports/clubs etc as well. Many, many fathers whose wives do all the family work have no idea at all how time-consuming, expensive, and career-limiting that sort of thing is. He may genuinely not have considered all of this. Nor how exhausting the bedtime routine, and planning a decent meal, can be after a day at work, nor how little freedom you have in the evenings as a lone parent.
If you can make it work, there are advantages for the children. Their father will be closer to them if he puts the work in, and you will have more ability to focus on your career again, so there are advantages for you as well. But you need to try to put the anger aside, and focus on what would work best for them, going forward.