Surely he’s not the only driving instructor in your area? Have a couple of lessons with someone else, it will be helpful to get a new perspective to see if you are really making the mistakes your instructor says you are making.
Otherwise it sounds like your instructor is making you overthink your driving too much. You do not need to be a perfect driver to pass your test or be able to get from A to B, you just need to be safe, have good judgement and be aware of what’s around you. The ‘mistakes’ you have pointed out seem like they would get you a minor fault on the test at most.
I would do some independent practice with your parents or someone else who has a license and a car if you can, and definitely try out a new instructor. You pretty much just need to get your test over and done with now. £50 per lesson and 100 hours is not feasible, and it makes sense that some instructors might want to keep you on for as long as possible so they don’t lose business.