Sad and Melancholy yet Beautiful

Melancholy itself can describe this. Sadness alone tends to imbue a sense of forlorn or general unhappiness. Melancholy often rings with a sense of beauty or serenity in the face of sadness.

In Russian, Тоска (Toska) describes this in a way. It's a very multifaceted and variant sadness that is often wrought with beauty.

Your initial "pathetic and beautiful mess" is actually really good, assuming that folk read pathetic literally rather than commonly. I can definitely envision that.

Could the word you're looking for be wistfulness? I've actually been looking for the same word recently. Poignant is another one I saw recently.