It doesn't have to sit flush against the wall. The 3-d look gives more interest to your space. Also consider wall mounting your TV. They make mechanical 'arms' that come out from the wall to angle TV's in corners such as yours.

I love the mirror. It will look amazing over the fireplace.

The mirror is beautiful. Im curious as to the color of the back of the mirror?

If it's black it will have a tendency to "stand" off the wall more visually, which is interesting. If you want it to visually push back then consider painting the back of the mirror the wall color.

What will the mirror reflect? Is it something you want to see two of?

I don't think that beautiful mirror will work over the fireplace. I think it will stick out like a sore thumb since you have no fireplace surround.