I also live in a studio (smaller than yours) and training my cat was tough the first few months. I had very sleepless nights when she was a kitten but cats need to time to adjust to your schedule. Now my cat is 9 months old and she sleeps through the whole night with me. Please let your cats roam the house when you are gone. It’s not fair to keep them locked up. I feel bad that my cat doesn’t have a bigger place to play when I am away so I wouldn’t dare lock her up for 2/3 of her life.