We need more pictures but right off the bat a new paint color, new lighting, and likely having to remove some pieces from the room.

A colour tip: red advances, blue recedes. Artists use that to suggest distance in paintings by giving distant objects a blue cast. So if you go towards blue or blue/grey walls, that should help right off the bat. Paint the whole wall one colour; if you like the detail of the chair rail perhaps you could paint that one or two shades lighter. But don't go for strong contrast.

Painting the whole room one color, or switching the order or dark and light colors on your chair rail would be a great improvement. I would put all 6 chairs around the table too, instead of the one lone on in the corner.

Totally agree with Rina, paint the whole wall one color and don't use strong colors. If you want to open up the place the lighter the color the better. You also want to draw your eye up so maybe lighting that is not hanging so low? Also, art work should be a bit higher to increase height.