Wow! Where to start!
1 If he wasn't paying the MINIMUM maintenance such that she had no choice but to go through cms then if/when you split he'll treat you and your DC the same
2 you may respect him now, pretty bloody hard to respect a deadbeat ex!
3 contact and maintenance are SEPARATE issues - children are not bloody pay per view!
4 do you know for a fact she has drug issues? Is unemployed? Or is this just what your husband has told you? Cos honestly I've a lot of experience with addicts and their kids tend NOT to be wearing £200 because the money would be going on the addiction! IF all you're saying was true your husband (and yourself) would have for the child's sake applied for primary residency, but of course you haven't.
5 what EXACTLY was the 'family based arrangement'? I'm guessing you mean PRIVATE arrangement he had with his ex. Was it the same as or more than the cms MINIMUM?
6 it's not 'us' paying the maintenance it's him. He has a responsibility to HIS child from a previous relationship.
7 the cms MINIMUM is a small percentage of HIS income. If things are so tight with him paying that then you maybe should have been more sensible in planning your own family.
8 did the money you provided for the 'extras' you claim REGULARLY meet the cms minimum? It's impossible for her to plan a budget based on money your husband MIGHT deign to provide.
9 the mother IS ensuring her side of providing for their child - with 2 DC of your own how much do you KNOW it costs to raise a child? Is your husband contributing 50% of that? I think it highly unlikely seeing as you're railing against the cms MINIMUM he's having to pay.
10 it's despicable that he's considering quitting working to avoid paying - total abdication of his responsibility YOU should be ashamed he's even considering that!
On one thing I agree, cms payments ARE unrealistic - they are woefully LOW and rarely come close to 50% of the cost of raising a child, even just basics.
Men who go on to new relationships in which they consider having more DC SHOULD first consider if they can afford to WITHOUT reducing maintenance to their older children - not to their ex's THEIR CHILDREN!
As pps I very much suspect the REALITY is he's been taking the piss for years, underpaying and now it's caught up to him! Tough! He shouldn't be an irresponsible father then (and I include your DC in this). You seem under the mistaken impression your husband isn't a deadbeat dad - news for you
He is!
If you split from him (increased likelihood in subsequent relationships) he'll be a deadbeat to your kids too!
Maintenance isn't used for "treats" it's for basic costs - do you REALLY spend less on your children than her for rent/mortgage difference for more bedrooms, children's furniture and soft furnishings, heat, light, hot water, food/groceries, clothes, shoes, uniform, school supplies, non-prescription meds/first aid items... ? Extremely unlikely!
Arrears - so he WAS underpaying!