Well, I was going to suggest the ubiquitous fiddle leaf fern, but looks like you have a cat, and they are toxic to cats. You might Google plants that are non-toxic to cats and see if anything grabs your interest. I think some palms may be ok with cats (and they can grow fairly large), or you might look for a contemporary plant stand and just sit a smaller plant on it -- maybe a giant tropical bromeliad or something along those lines. That said, if your cat is prone to pester plants, it's probably not a good idea to include one in your décor. (Definitely don't put a fake plant in this pretty space.)

How much money do you have in your budget? If you want to go for broke, get a Miele combination steam oven with an extra large XXL oven cavity, and a Miele Speedoven with a regular oven cavity. If I recall correctly, stacking those two units will take up 42". Have a small filler strip made that makes up the remaining 4.5". Either match the stain of the wood, or clad the strip with stainless steel to match the appliances. Or even better, have a carpenter put in a shallow drawer. This will make the kitchen extremely functional. If the new homeowners like to cook, they'll definitely appreciate it. Unfortunately, it also costs a lot of money. If you plan on living in the house, then that makes sense. If you only want to do this for staging, then it is way overkill. There is a good chance that the home buyers will rip out appliances anyway and install their own.

Pull the sofa back to where the wall angles in the "empty" part of the room. Add a couple of swivel chairs on either side of the fireplace, facing the sofa. Place a sofa table behind the sofa, with a couple of lamps, to give some nice light to the room and further visually fill the empty side. Get a much larger rug, and a larger, round coffee table.

Well it depends on the size of the transom. A traditional transom will not. if it is a larger and or operable transom possibly. A lot depends on your ceiling height as well as the outside elevation with that. If light is your goal you can do both if it works on the outside elevation. Also you can do a regular size window inside a shower. Or two smaller square windows.......the possibilities are endless but I try to not elimate existing windows where possible especially when it gives the opportunity for function and light. lower cabinets although tall ones.....i would go counter height with window above.