IR35 - Appropriate tactical date to make New Child Maintenance application

Good evening everyone,

I am going through a divorce having separated from my husband last year.
I would like some information please. My husband is a director of a limited company and currently files annual tax returns. I have now found out through his disclosure as part of the financial proceedings in divorce that he pays himself minimal salary around £750 per month and claims minimum dividends in the region of £25K annually. If I am to apply for child maintenance now (29th March 2021) I know I will not receive as much for our children he is staying with them every other weekend only.
With the introduction of IR35 on 6th April 2021, he will likely have no choice but to work through Umbrella companies/ PAYE which means his monthly gross will likely be in the region of 7K before umbrella company deducted their fees. After tax and NI he will likely be in the region of £4.5K net per month. He will not be a happy man even to receive such 'low wages' gone are the days of tax 'avoidance'.
I would like to understand, should I rather wait until after 6th April 2021 e.g end of April to contact CMS so that when they contact HMRC there will be PAYE monthly gross reflecting through payroll? My concern is if I start before 6th April they will use his last years tax return figures that only show dividend of £25K and minimum wage salary.
Shocker : he currently transfers £200 per month for his 2 children!!!

I appreciate your assistance in anticipation.