I would love it if you could take two more pictures. Take a picture from the left corner and then from the right corner of the wall where the fireplace is, pointed towards the dining room area. This would give us a better idea of the space. I'd love to help you!

I think that a built in bench seat with storage would look great under that window.

I think your furniture placement is good so far. Perhaps add a two chairs slightly on the side of and in front of the fireplace. You could do so many things with those windows! I'd go custom, if it is in your budget. Visit a drapery showroom for great ideas.