I think this couch would look great in your space
http://www.bryght.com/product/191/helsinki-modular-5-seat-sectional-with-ottoman

or this one if you don't need as much seating
http://www.bryght.com/product/190/helsinki-modular-4-seat-sectional-with-ottoman

Unfortunately, it's not going to ever look good separated.
Can you eliminate the wedge entirely? It looks like the arms will remain intact on the other two extensions.
I would break it up visually with some throw pillows for now.
Replace it with something else down the road.

TV over FP and eliminating the wedge will solve your issues with seating. Move one sofa on the present TV wall and "L" the other with it to face the FP. Fill the inside of the "L" with an area rug so front feet of both sofas are on it and it extends about 10" past the ends of the sofas. Add a round coffee table, one end table and lamp and one floor lamp. Your Victorian swags are way out of place in this casual family den. Take them down and re-photo at night so we can advise. Are these west windows? Looks like you could rethink the lighting fixtures as well.

IF you need the wedge for seating, but not for watching tv, it could go in the corner to the left of the fireplace and a fun little table put beside it.

It doesn't look like a sectional to me. It looks like a sofa and loveseat (with the arms on each end). I'd lose the wedge and get a chair instead.