Corner fireplaces are the bane of Houzzers, and we deal with the frustration of many who can't arrange furniture around them. I suggest you buy a bargain electric FP on black friday and move it around the room, trying it at different outlets until you find the place where it is perfect and your furniture can be focused around it. Don't get one made for the corner. This is just a trial, so you want a flat one, and you can span corners with it to try it out. Once you decide and build the real one, sell the trial FP on Craig's List or use it in the master bedroom or other location where you want a bit of romance.

On that note, you might look at media consoles that have an electric fireplace below. They've come a long way! Then you could just replace your existing console.
Electricfireplaces.com-

I would not get a sectional. Buy a new sofa and 2 comfortable chairs. Do not get all leather. Either the sofa or the chairs. A table behind sofa, move it out from against the wall. Same with the chairs. An 8x10 rug and a coffee table or ottoman. IF you want a FP put it against the short wall opposite sofa. Get a large picture for the wall behind chairs. Hang all pictures so that middle is at eye level. Put 1 lamp on sofa table and the other on end table next to sofa. Floor lamp in corner behind other chair. Down scale the chairs a little bit. The ones you have are huge.

This one is 45" wide. Measure your wall and check out overstock.com for electric fireplace

I would not put TV over FP.

28" wide