Hard to know without the actual figures.
Although even without having a joint account I would expect a FAMILY to operate as if all income was FAMILY income.
Based on my own bills pcm IF I were working they would be:
Council tax 92.00
Gas 95.00 (don't get me started!)
Electric 40.00
Sky (I don't have but min package on looking up but not Inc offers) 25.00
Total 252
Food (based on my budget but calculated for 5 people) 400.00
Clothes (rarely bought I'm estimating a min for 3 growing children + op not inc shoes) 100.00
Books/toys/activities/clubs for 3 I'd estimate min 150.00
That's 650!
So you're paying out likely almost 3 X more than him and he's the higher earner by almost 50%? Wtf?!
Then you posted your own figures
He pays 400.00
You pay
Food (min) 400.00
Clothes 150.00
Gifts for friends (based on approx every other week at £10 a pop min) 260.00
Dental treatment - I dread to think!
Cats - no idea how much cats cost I'm guessing at least 50.00 for food
That's 860.00 minimum!
"we moved house last year, I paid for the move & extended my overdraft in order to do so" why?! He was getting a free home! The least he could do is pay for this!
That's £2549 per month in take home he's getting and after bills he still has over £2000! That's purely his spending money!
If you split and even if he had the girls overnight once a week he'd be having to pay £125 a week maintenance that's £541 a month - that's MORE than he's paying now and now he's using the house, gas, electric, food, cleaning products, toiletries...
I don't think he's even covering his own costs!
Financially you'd be far better off!
What kind of father pays NOTHING towards their own children even when they're living with them and they're on a bloody good salary? It's neglectful if not downright abusive!
Unless there's a MASSIVE change in his behaviour for the better he needs to go. I think it highly likely he's COSTING you money rather than contributing anything it's appalling!