If you don't choose a solid black background, it will be necessary to artistically create an edge around the lady which doesn't presently exist. And I fear you don't have the necessary Photoshop skills for that very difficult task yet.
I urge you to stick with black for this one.
You've posted in Brian's section, and that was a wise move, because this is definitely a question for Brian.
I expect he might like to know what camera you have at the moment?
Gosh, that sure is unusual.
Usually you can drag the panel around, and it'll "snap" into place.
If yours isn't doing that, I fear you'll need to go to Window>Workspace>Reset Workspace, and start over.
There's nothing can be done about focus, I'm afraid. It is what it is.
For the background, I figure plain black would be best - is that what you were thinking too?
Well, why don't you try it and see?
Add a Levels adjustment layer, and move the white Output slider on each of the three channels thusly:
Red 210
Green 130
Blue 235
Then mask it very carefully to the dress.
That's right. If 90 is still too bright, calibrate again at 80. If that's still too bright, try 70. If 70 is still too bright, there's DEFINITELY a problem with your room lighting.
Let's not worry about that for the moment. We'll concentrate on getting the brightness correct first.
So that we don't get bogged down any longer, let's pretend this is ok, and press on with the glasses issue.
But you have a BIG problem. PLEASE don't wait any longer to take the Raw Class, I beg you.
Now can you give me some 100% crops so I can see the glasses problems close up?