It's a little hard to get a sense of the layout and scale from this one angled photo. However, in general you might look to put a couch with its back to the doorway, so that there's a "hallway" running behind it into the rest of the house. If you don't have space for that, then just creat an entry *zone* just inside the door, with a table and small drop zone, and otherwise arrange the living room however works.

Can you share a layout of the room with measurements? My first thoughts are why isn't your seating facing the TV and do you need more seating when you have a large sectional for two people and a dog.

If accurate in your drawing, I am assuming you are leaving the space behind the sofa for a walk way. I’m not in favor of that because everything is off-center. Position the rug directly in the middle of the room, sofa on long wall, love seat under back windows and to balance the two seater on the other end, add two chairs. Ikea piece to the right of the fireplace and something above it to balance the window. Remove the brown table left of fireplace and add a smaller Ikea piece in white for this effect: (except mirror goes over larger piece).

I would use the den as TV area with TV between the built-in bookcases. Then do a back-to-back arrangement with two sofas (they don't have to match) and a rolling sofa table between them. The one in the den would be the guest bed. When you have guests, simply roll the sofa table under a window and close the sliding door. As an office, place a desk facing the window if you need good light for online conferences, or put it on the wall if you don't do that. A rolling desk chair can move out of the way for the sofa to be opened. In the living room side, use a round dining table in the corner right of the fireplace. A coffee table 12-18" from the sofa and perhaps a pair of small scale upholstered armchairs in an "L" with the sofa, their backs to the window. Art, not TV, above the mantel.