CMS variation form

Help - has anyone ever successfully done a CMS child maintenance variation form?

My ex runs his own ltd company as sole director, has a second home and yet pays based upon earning minimum wage. I asked for a variation a couple of months ago and explained the situation in writing, and they have finally sent me a form to fill in. I was expecting them to check his tax returns on HMRC and now I'm confused.

I don't know what he earns in terms of dividends, and it seems crazy to guess. Do I just put down what he earned when we were together?

They also ask things like if he diverts money, and give examples like overpaying to a pension and keeping money in a business account. But I don't know what counts as overpaying to a pension - he used to pay £300 a month which is a lot given he currently only gives £130 a month for two children, but maybe its not legally seen as 'overpaying'. I can get info on his business bank account from companies house but it seems daft for me to need to do that myself.

He uses his work truck for all his personal driving now and I don't know if that's relevant?

The other issue is that I was legally 50% owner of the business until Mar 2019. As we split in Feb 2018 he didn't take any dividends in the last financial year at all to ensure he didn't need to pay me anything too. So he must have had a much higher wage last financial year and then have dropped it down to minimum again just before the CMS claim went through in April. Does this mean he'll get away with still paying based upon min wage for this current year and no dividends (as these are based on the previous year).

Any tips on how on earth to fill in the form??