The furniture under a TV should be 25% wider than the TV itself. Here's a chart to help you figure how large a TV and credenza under it you need.

Curtains should hang like this.

Seating should center around your double focal points (TV & FP.) And husband feels the view is another focal point. Would you consider closingmost of the double arches and going for one double door sized opening? Forget a loveseat; they're a pain to deal with, only seat one and booger up most arrangements. A sofa and two chairs plus coffee table is really ll you need for the seating. I would close the room more, float the sofa facing the TV wall and place the two chairs either side of the coffee table, or on the window or wall side of an "L" with the sofa.

Rug on angle, sofa on angle, t v on a much larger and better looking console, or do a built-in. IKEA has some great, affordable ideas.

Tell hubby a designer says do not leave those windows as is. They look sad and lonely and dying for some attention. Triple windows are a gift to a room.

This might be a drastic step, but would solve the furniture placement problem and also, I feel, would make the room flow better and give it a coziness. Build a pony wall between the first two posts. You could put a piece of wood on top with rounded corners cantilevering a few inches into the entry.

This will allow you to place furniture against the pony wall, which is what you are lacking in this room, wall space. You only have one wall for a sofa, to the left of the FP. Where the brown sofa is now blocks the FP and is not ideal for TV viewing.

I understand not wanting to block the window for light, but is there a view out there that you often stare at?

If not, you could put a low back sectional, or sofa and love seat on the window wall and the wall opposite the arches. Or on the window wall and the pony wall. Then the TV on the wall to the right of the FP. This would give you the best TV viewing. And also open up the middle of the room making it more inviting to walk into. You could tape a white sheet or a piece of cardboard in between the first arch to give you a feel of how it would flow. Height of wall might depend on what you put against it. I would guess between 36" to 42". You could hang 1-3 small battery operated sconces from the top of the arch, or hang a plant. Also, if needed, you could put a bench or table on the DR side. I wish I could photo shop better, perhaps someone here can mock it up. I think that a pony wall could be built and possibly attached just on the sides of the arches, leaving the carpet and hardwood untouched. Of course it would have to be sturdy enough in case kids try to climb it.

Just a thought, it would give you so many more options with out, in my opinion, losing anything. After looking at the photos again, it might be that the room next to the LR is the kitchen. And maybe that openness is important. If that's the case, ignore my comment.