Your humans need to attack this diligently if they want to control your scratching. They should cover every surface that you scratch with something that you won't like to scratch, like foil. They should also get you more scratching posts. Have them get several different kinds and put them all over the house. The idea is to break your bad habit by replacing the inappropriate places with appropriate places.
Some humans use squirt bottles and squirt water on the kitties when they scratch.
You would probably chew them off. As for the problem of getting your nails clipped, I hate that too. Ask you Mum to be satisfied with one or two nails at a time, to move slow and easy, and to have lots of treats ready for when you are good. Maybe you can learn to let your nails be clipped if they reward you and don't frighten you by trying to hold you down. Your final problem has only two solutions.