I wish I could edit my post:(. I think windows are on all sides.

A 60" round table would work just fine in the space. Better to have some open space around a table and chairs than have cramped furniture.

I have large chairs and can just squeeze 6 chairs around my 60" round pedestal table. Leg design/position and chair size will determine how many chairs you can fit comfortably.

What was the plan ?? To me this is ahuge wasted space not with any thought as to how to use it IMO breaskfast nook is a place where a few people at a time grab breakfast . Is this going to be your actual daily dining space then you need a nice large table and chairs for dining not grabbing a quick breakfast on the way out the door. I agree a 60" round seems logical we have no clue as to how many seats , it is also atraffic area to the outside that will limit the size of table too and that will be decided by how you want to use the space .I see counter seating in the kitchen so I need a lot more info as to what you really need in that space . Post all that here in comments too.