The issues of support for yourself and support for your children are separate issues.
He is required, by law, to pay child maintenance to you if you are the main resident parent. This is based on his salary, calculated as a percentage of his income.
The link here is a calculation tool that is used by the CMS to work out how much he should pay each month: https://www.gov.uk/calculate-child-maintenance
As to whether he has to support you financially, this is dependent on you making an application to court as part of the divorce.
You can ask the court to award you interim spousal maintenance (it's called maintenance pending suit) if you are completely dependent on his income. You have to show the court that you need this support to survive.
The court would then decide the final position at the point the divorce is completed.
But, you don't get spousal maintenance unless you apply to court, so you would need to get the ball rolling and any financial order application has to be proceeded by mediation (a mediation assessment is a legal requirement prior to making the application).
For a family mediation service, see here: https://www.familymediationcouncil.org.uk/
The link here is for a divorce application - you can ask that he pays these fees (£550): https://www.gov.uk/divorce/file-for-divorce
And this is the application you would file for interim maintenance from him (along with all other orders relating to joint finances/ property): https://www.gov.uk/government/publications/form-a-notice-of-intention-to-proceed-with-an-application-for-a-financial-order
I hope that this answers your question?
Thank you for your enquiry today. I am happy to answer follow-up questions - please do get in touch with requests for extra information or further queries and I will do my best to help you.