I have been paying several hundred pounds a month in maintenance payments for nearly 3 years to my ex-wife who still lives in the family home which costs £500 less a month less in mortgage payments than my rent whilst she earns in excess of £10K more than me. I have always disputed her right to impose the ratio of nights with the children but without taking the children through the court process I have had to accept it because of her refusal to engage. Is the crude 'nights with' calculator the only means of measuring maintenance payments as it seems so unfair?
Unfortunately the overnight premise is the way they calculate amounts.
The court process is generally quite manageable for children, it's up to the parents not to involve them in the ins and outs of the proceedings, so it shouldn't affect them adversely, if you decided to go ahead with it. Personally, it wouldn't stop me from fighting for my children's right to have me fully involved in their lives.
All the best
Just to add, whatever you do, don't make the case about the level of maintenance, keep it focussed on what is best for your children.