Windows are sized differently by different manufacturers so I have assumed the sizes you specify are frame/unit sizes. The numbers you mentioned do not add up to the ceiling heights so you might need to review and correct them. For instance on the first floor 18 + 60 + 18 = 96 which is a 8 ft ceiling ht. instead of 9 ft. At the rear first floor 12 + 60 + 12 transom + 12 = 96 which is 8 ft instead of 9 ft. Interior stool heights of 12" and 18" make rooms difficult to furnish unless they are very large and it increases the cost of the windows for tempered glass in the lower sash. I can't comment on inaccurate dimensions but I would suggest you make the windows wider than a 30" frame size unless you are trying to make them look like historic colonial windows which IMO are really too narrow for modern houses. And if you want them to look authentic, the shutters should be 1/2 the width of the windows instead of 1/3 as drawn. The panes should be taller unless you really want the them to be about 7 1/2 x 8. That would make sense if the panes were 4 over 4 in a larger window. Putting brick up to the height of the garage window sills is an architectural joke for a traditional colonial house. In a traditional house cladding material should change at floor lines as if they were real rather than simulated.

i wouldn't make it an all or nothing question..i would weight all the pros and cons..first..how often is this room used for dining, if it is used more than 8 to 10 times a year then consider it a dining room and then pay attention to the safety of the guests and the floor..but if it is an only occasionally used for large meals type room, then consider how you want it to be. You can always put some felt circles under the rear legs of the chairs so that they are not scratching the floor if you like the rug and keep it. my rug in my dining room is NOT large enough to be under the rear legs of the chair, there really is no proper way to use a larger rug in this room, and so we leave it. We only use the rug for large meals occasionally and no one has ever noticed or if they have they haven't said anything. we use the room ourselves, but not for everyday eating meals, we use it for other things..as well..conversation, working on paperwork, etc..but we don't feel the need to replace the rug.

I don't think I will be covering the windows, although I may change my mind once we live there for a bit. I have a round black leather coffee table ottoman that I may use but the other elements of the room I will work in based on the furniture that's on order and the rug that I choose. I agree that I don't want a rug that is too light or shows marks easily. This is a room that will be used everyday.

Another way to find rugs that gives you an infinite array of choices..is online sites....the most agreeable one to me is Wayfair....the only risk is that color may not be exact on arrival....the prices are much less for equal quality...and returns are pretty easy ...when I was looking for a big rug I ordered it is a very small version to see the color to save time ...they are usually useable on your home as beautiful door mats,etc. or you can return them on their dime....I usually buy hand tufted as I like finish better than hand knotted...as well they are mostly lower in price....finding the perfect rug the most challenging step in your process... but i can offer my experience of having rugs in my home that I bought 30 years ago and still love ...so it is worth the effort