Firstly I'm not a professional, just someone who has messed about with positioning and room treatment for the last fourteen years or so.
I reckon you've probably got the best arrangement that's possible but could move things about a little. The disadvantages you have are the open space on the right but an advantage is the space you've got behind your sofa.
My idea would be to position everything as best as possible then use room treatment to correct the problems.
If you can it would be best to pull the speakers out further into the room. When I say further out I mean by about seven feet from the front wall and three feet from the side wall (using an extended line from the kitchen wall to the front wall window)! Your speakers will now be about three feet apart! Your sofa (your ears really) will be about seven feet from the back wall. That is, by looking at the Living Room area of 20' x 10' and using this 'The Thirds' concept:http://www.barrydiamentaudio.com/monitoring.htm
If you can't have the speakers there permanently, consider moving them there just for listening then storing out of the way when not in use. Try the position any way to hear what it does. 'The Fifths' would be pretty good too, and perhaps more practical.
For room treatment, the left side has corners that will affect bass. I would think a couple of bass traps in the left corner would help, but bass traps are usually large and not pretty (and, is that some sort of vent in the corner?). Bass traps can go in any corner - wall-wall both back and front, wall-ceiling and wall-floor. I don't know which corners are the most effective. If they are equally effective you will have more options. This might be a question to ask.
With side wall reflections, some people like them, others don't. I think you will get reflections off the kitchen wall if you adopt 'The Thirds' (or 'The Fifths') so you now have symmetry here. To prevent reflections (which I now prefer) you need some absorbent panels at the specific points of reflection on the walls, or, standing on feet beside the speakers. These can be decorative - you can submit your images for printing on the cloth that covers the panels.
If room treatment, or some of it like bass traps, is not practical, you could use Digital Signal Processing (DSP) or an equaliser.
I use all three methods: positioning, room treatment then EQ to finish off.