Your whole relationship/ financial setup stinks.
He gets to work full time because for some reason even though they are his kids, arranging childcare is your responsibility
He gets the weekend off childcare and chores while you work
You're constrained by his working hours so only earn a fraction of what he does but have to pay an equal share of the bills
Despite doing all the childcare in the week to save 500 quid a week and working all weekend, effectively giving you no break at all, you still manage to fit in the entire list of chores into the time between your work and looking after your children.
Despite you giving everything to him in terms of time, workload, and money, he doeant appreciate it at all and refuses to lend you money and sits back when you're struggling and buys himself a present.
I know depression can make you selfish and lazy...but has he always been a bit like this? I will stand corrected if he previously did 50 50 and was generous with his money but honestly lots of people are depressed and don't treat their family this badly.
You really need to start looking after yourself as well otherwise you will become so tired and worn out and resentful that when / if he gets better there will be no relationship left, and becoming depressed yourself is a real danger.
You need equal spending money and a bit more time off just for you to relax or whatever. You should be looking at equal 'downtime' when he is better. I'd start with the finances, you work much harder than him and deserve equal 'spending money'. Don't let him being moody, let that sway you, as that's very manipulative