It's tough to tell for sure without seeing your whole layout, but at first glance it looks great and not too big at all. Remember that when you have a table and chairs, it needs to be farther from the wall than when you have banquette seating, which doesn't need push-back room. So, I'd be afraid that a table with all chairs would feel even more crowded to you. If it's an option, I'd certainly wait until the cabs are all in and the table arrives to make a decision. I think there's a good chance you'll love it once you get used to the way it feels.

OSH, I think her sofa is beige microfiber. See it in the chair link posted above. Are the leather chairs posted above the dark brown, or are they black? I can't quite tell! Personally, I'd prefer a slightly lighter brown color with that wooden trim on them, or check the color of the leather chair in my living room below. Are you working toward a monochromatic color scheme in this room? You mentioned possibly getting a tan rug in your chair post. Do you plan to bring in prints and more color in accessories? I think the room would really come alive with more color. I'm a huge fan of browns and beiges, but my LR, while having those, also has more color. I think a patterned rug would be great, and bring the room some warmth and depth.

I know you didn't ask and I'm the least knowledgeable in this aspect, but I think the light color of the upholstered chairs is what makes them seem so large and imposing. I definitely prefer them at the ends of the table, both size-wise and because the hosts are important. It's true. :) But they seem much larger in their whiteness.

The only thing you could do with the walnut is use a black stain. For the stain to take evenly there could not be one speck of sealer/varnish remaining on the surface. Completely stripped clean. Leave them as they are or risk messing them up.