Congratulation on your purchase ! This is a beautiful room. How wide is the fireplace? Your TV shouldn't be wider than fireplace. Tape it out and see. If you can comfortably watch 50" TV that would solve your dilemma. You can balance out an extra-wide TV by placing two bookshelves on either side of the fireplace. The bookshelves should be at least as tall as the fireplace mantel and at least a foot wider than the TV extends. But I feel that 75" is just too big.

Look into the Samsung Frame TV. It looks like art when it’s off. I have one in my bedroom, it’s pretty awesome. (Good tv too, so not just for the art)

My TV is above my fireplace, and it's a bad spot. You have to crane your neck or support it to look up. TVs are better placed lower down to the floor.

I would move leather sofa in front of fireplace floated- so you could walk behind still. Move oversized chair table to where sofa was- angled toward tv. Loose the big bulky tables that aren’t needed and get one smaller side table for a small trim line lamp a standing lamp between the 2 windows possible. Get a round smaller coffee table for in front of couch. In future I would downsize big bulky chair for 2 smaller accent functional chairs you could set side by side or one on each side of fireplace facing each other.