Hello Jayne, What a fun space! Here are a few of my thoughts: For the dining space, I would stick with a small, rectangular table. Because you have a doorway to the porch near the dining area and you want room to walk around easily, I would aim for something not larger than 60" long by 36" wide, but you can double check that in the space. As for the seating area, if you want to maximize seating, I might aim for a couch with one or two chairs along the wall with the window. I notice when I have guests, everyone chooses a chair. Not everyone wants to snuggle up next to someone they don't know very well on a sectional. It is also easier to rearrange if you decide to change up the layout. If you want to have even more options for seating, it might also be nice to do one or more ottomans that are cushioned and could be used for feet or as additional seating for guests. They could be grouped together or spread out when being used. If you ended up replacing your coffee table with a/an ottoman/s, you may want to also add end tables so there is a place to set drinks, remotes, or lamps, if desired. For an entertainment center, I would potentially choose something a bit more narrow to make sure it wasn't in the walkway, For instance, this entertainment center is 14" D so it is the same as the depth change in the wall so it could be flush. I can be clumsy and prefer to have things tucked away or I run into them! Then I would add a rug, some lamps, and maybe a great mirror over the fireplace to make it look bigger and brighter! Good luck with your decorating and please share after pictures when you're done!

The first sectional is 100” x100” not 7.5’ your room is only 120” wide so no to that one the orange one would be better but it depends on how you place it and IMO no better than an actual sofa for seating 2 people can’t fit on the chaise .Samr for the last one. Look at sofas instead, get that then see how much space you have you could maybe add a chair or depending on the sofa maybe 2 small chairs . Your dining table needs a min of 36” for the table and 24” all the way around for chairs so that is 7’ x 10’ That will pretty much fill your space . The easiest way to try out pieces is to cut them out of cardboard to scale and play with them in the space when you place measure the walk space then try that out in real life on your floor. IMO you need 36” walk spaces . Use graph paper for the main to scale floor plan it makes it easier to figure walk space.

I like your proposed arrangement. Looks like you could add a t.v. on a swivel mount with a small console underneath to the right of the fireplace. As a general rule, the rug under the dining table should be 4 feet wider and 4 feet longer than the table, so it seems an 8x10 would best suit the table when fully extended.

If you want a TV in that room the only place it can really go is to the right of the fireplace (maybe to the left if you find that works better for you). It is never recommended to put it over the fireplace unless there is nowhere else for it to go. You have more than enough space on the right for a nice console. Maybe in the future you can do something more dramatic with the fireplace as it looks small in that large wall (or maybe you are already and it's not finished yet). Put a tall piece of art over it (something that is less wide than the fireplace). Face your sofa toward the fireplace and TV. The dining table should have the long side parallel to the slider. I can't imagine it fitting the other direction. I don't think it's a bad thing to have your old furniture in there for a while. It will help you get an idea of the right size for new pieces. You may also get better advice if you post a graph paper drawing of the space so the commenters know exactly how much space you're working with. The perspective in pictures is sometimes misleading.