A "perfect conclusion" depends on the point of view of the reader. Some readers might think Paul's suicide is the best ending, or perhaps the only possible ending. If you are the kind of person who wants a happy ending, then you must consider what else could have happened considering the circumstances of the story.
First, let's look at Paul's character. He considers the world around him to be ordinary and is totally unacceptable to him. He considers the world of music, the theater, and art to be glamorous and exciting. Paul wants everything money can buy, but he doesn't want to earn it through hard work. He is thrown out of school because he consistently lies, refuses to do his work, and shows disrespect for his teachers. His next move is to steal from his employers and take the money to New York City where he stays at one of the finest hotels, buys expensive clothes, and goes to the opera. He is living the life of his dreams and seems to have no remorse for what he has done. When he discovers his father is coming for him, he chooses to kill himself rather than return home with his father.
Let's think about why Paul kills himself. Is it because he can't bear to go back to the ordinary everyday life he ran from? Is he just a mixed-up kid who doesn't realize the finality of his act? Is he so removed from reality that he can't imagine living in any other world except the world of his dreams? The author leaves it up to us to decide his reasons. It could be one or all of the above.
Now consider what else could happen when Paul finds out his father is coming for him. Perhaps his father now realizes how troubled Paul is and gets him the help he needs. Maybe he's discovered to have unbelievable artistic talent and realizes his dreams. Remember, whatever ending you choose must remain true to the story and the characters when you consider what you think the "perfect ending" might be.