Yes. This form can be used to emphasize that someone performed an action. It was you (and not Larry) who broke my vase.

Yes. It is correct. You need to put some kind of punctuation at the end of a sentence, either a period or an exclamation point. You use this pattern when there is a list of people who might have done something, and you are discovering or identifying one of them. If you see me break your vase, you say: "You broke my vase!" If you discover a broken vase first, and later realize that I broke it, you say "It was you who broke my vase." One can imagine a grandparent saying "I love all my grandchildren, and I remember things about every one of you. Why, it was you, Ruthie, who drew pictures on the wall with a marker. And it was you, Charlie, who tried to flush a baseball down the toilet. And you, Mary, it was you who broke my vase."

I never touched your vase ! But seriously, yes you can say that. "It was you..." or "It was your..." can proceed all kinds of accusations. Check it out, https://youtu.be/Ec8h_DojbMQ?t=73

If you were accusing someone of breaking your vase, or they were denying they were involved, you could say 'it was you who broke my vase' or simply 'you broke my vase'.

Attention! I'm no native, so take it with a grain of salt, but I'm fairly certain that you can indeed say it like that. In fact, I believe it's very good English. For example, this is something you might want to say to someone who refuses to accept their guilt.