Selling the door gives back every lock on the door.

Selling the door should give you all the locks back. There is no way to take a certain amount of locks off other than selling the door and manually putting on what you want back on.

Patrick J Fox wrote

Tile says it all

Lockbreakers break locks on someone elses door
selling door gives you all locks back

I can see why you aren't able to remove locks manually though. By selling the door you have to pay the 10% fee so its less convenient to do this BUT if you were able to remove locks people wouldn't leave their locks on their doors unless they were online so that other couldn't break their locks.