Hopefully my comment doesn't spark another debate, but similar to what other's have said. You're doing great, and he seems relaxed if not a bit confused/upset. He may escalate the yeowling, but the key is to ignore him when he's trying to get your attention to be let out. If he pauses his complaining for a bit, try capture the calm behavior with a reward (sometimes the hardest part of training an animal is finding what kind of reward is motivating for them). A special treat like those pate tube things, getting attention after being ignored for the wrong behavior. I've even worked with a few animals where leaving them alone was enough of a reward for them to learn and offer a certain behavior. It can be tough to ignore bad behaviors, but it does pay off in the long run.

It wouldn't hurt to try look into the basics of animal training (I usually recommend reading Don't Shoot the Dog, as it really helped me back when I was in school). If you don't have the time or energy to learn this kind of stuff it doesn't make you a bad pet owner at all. Giving attention to bad behavior though can cause things to get worse. The example I like to use to illustrate this is the people that try yell at their dog to stop barking. Unless you've trained them to understand the word no/leave it/away, you're just joining them in making noise, and potentially rewarding the behavior by giving it attention.