Right, I have read all of your answers and now want to say sorry. However, you did not word it well or explain it well at all.
Your husband is a dick. It doesnt matter that he is 'so good in many other ways', this is financial abuse.
You need to work out all of your bills and split it so you are both left with the same amount each month. In a marriage, one person shouldnt be left with £1000 each month while the other has absolutely nothing. If your car needs fixing then this is also a joint cost. Savings are joint savings because there is no ability to save money if the other isnt contributing.
He needs sitting down and telling. He also needs telling that what he is doing is financial abuse. You need to change how things are done or he needs to go. If he went, you would get universal credit (or something, im not sure, take advice), you might even find you are better off.
This is way more than an issue about a £5k gift from his parents. I cannot believe you havent lost your shit with him over the split of money. I would absolutely not accept this.
I do think you need to look at alternative incomes, even if you have to work a few evening a week in Tesco, it will top up the JOINT income too. Although if he is £1k spare a month then you probably dont need to.