Privacy could be obtained with a screen, placement of potted plants, an open bookcase, but I like your idea for a curved track with a curtain as one option for visual privacy. I would rotate the dining table 90 degrees and move it towards the balcony. I would remove those two chairs/tables because the layout of a single chair that far apart from another chair does not work. You may need to move the seating away from the main entrance because it looks like you walk in and you're on top of a loveseat. In such a tight space with so many doors that open in to the main living/dining - my advice is to keep it simple. Scale the furniture properly and have pieces that are multi-functional. Example- an ottoman that can serve as seating. A bench at the dining table to seat 3 on each side. I would also place two smaller loveseats facing each other in front of the fireplace. This will give you an "entry area" (along the back side of the kitchen wall) and help to define the living from dining rooms. Even if you don't have a formal entry, try to create a bit of space to welcome people.

Leather sofas can really dominate the room and can give an overall cold feeling. I would add some earthy elements, like a wood coffee table with glass or metal. Go to Restoration Hardware's website and look at their sofa room scenes. And I'm sorry I think the art is too harsh for the room. That's all your eye goes to in the room. too overpowering. I would look for something softer or maybe a cool mirror and I would add color to the room with pillows and some colorful lamps. I also think woven blinds would look great. They add warmth and give a finished look. The color of your window treatments should contrast your wall color a bit, not match it or else it starts to look generic and blah.. You have warm walls, warm floors and the woven blinds, like Hunter Douglas brand would pull it all together for you.

I agree with divadeva. More lights. If you can add pot lights do it. If they're already there add task lighting and up the wattage on the bulbs on the pot lights (replace with LED and you can make them brighter because the wattage on LED is lower for brighter light). If you have all of that add decorative lighting. If ventilation is an issue find a way to move the air around or add air filtration. Maybe the HVAC is deficient. Maybe you can add a HEPA filter instead of the standard one that comes with the unit. Call an HVAC specialist to see if there is a way to boost air flow in the room.

I feel partitions are not needed. You already have too much for the space. Adding a partition will shrink the space further. The simplistic solution, you do not wish to discard any furniture would be to paint all the walls in lighter pastles. And use some wall painting frames to highlight certain walls.