I had a weird landlord too who wanted to keep some money under the pretext of wear and tear. It's a classic thing unfortunately. So the law is clear: normal wear and tear is on the landlord. Small marks on the walls, light scratches, wallpaper discoloration after years, all that's his problem not yours. He can only keep money if you caused actual damage (hole in the wall, broken tiles, damaged flooring, that kind of stuff). Nail marks or light traces, that doesn't fall into the "damage" category.
The procedure is that he has to return your deposit to you within two months max after you move out, unless he gives you a detailed inventory with photos and clear justifications for each deduction. If he keeps money without proving the damage to you with quotes, that's abuse. Ask him in writing (email, registered letter) to justify precisely what he's keeping and why. If you have photos of the studio when you moved in or out, keep them as proof. Honestly since it's just marks of nothing, he has zero legal argument. Push pretty hard on the fact that normal wear and tear is his thing, not yours.