He will insist that the children are quiet at meal times so that he can always listen to the radio or TV. No. This is terrible manners; TV and radio off at family dinner time. He can live without it for an hour. If there's some special occasion where he needs to hear/watch something live, he can do so on his own rather than inconveniencing everyone else. Starts shouting if this rule is not upheld. Not pedantic, but a bully. And it's unreasonable to expect another adult to abide by a rule they didn't agree to.
Is obsessed with feeding the kids healthy meals. Over the summer, they are allowed one lolly/ ice cream a day. They have never been to a fast food restaurant as he would go mad. If I ever buy sweets, he goes ballistic. Healthy food is great, and one treat a day seems reasonable. But again, he can't just control everything; the two of you need to decide this together and compromise if necessary, don't undermine each other and argue in front of the children. No one should be going mad or ballistic over this.
Is obsessed with his mpg in the car and if I’m driving, will always tell me what to do. He needs to back off and let you drive when you're driving and vice versa, unless someone's breaking the law or putting someone in danger.
Will not let me do laundry during the day - it has to be done during the night to save money. He can do all of the laundry for the household if he wants to decide for everyone when it gets done.
Will never, ever chuck anything out and when I try to have a declutter, will go through the items and try and bring things back. Is he a hoarder? Does he insist all of this stuff be out, or could you put it away/in storage?
When in the car, he gets fixated on overtaking the car in front and drives too quickly with the children. Obviously not OK. If he can't control this, he doesn't drive you or the children.
So far, it seems like he's at least a large part of the problem. And nobody should have to live with this.