I can see 3 spaces you could do nicely. 1) a dining area right off the kitchen half-wall 2) with the tv over the fireplace, you'll need seating opposite. You could have a loveseat and side chairs facing that focal point. They probably would need to be flush against the wall instead of leaving a walkway behind them, unless the room is wider than it looks like. 3) In the front corner, you could have an l-shaped seating arrangement for a conversation corner, or a home office/workspace, or a piano. You wouldn't be able to see the tv from here at all.

i would not place over the fireplace, that is too high. you can put on an arm on the left side of the book case where the slot is for a smaller one or leave on the wall it is on, then i would give it a larger console. i think i would continue to have the sofa face the fireplace then have two swivels on the right side of the couch so they can turn to the fireplace, the tv, or the couch. i would not even ask about shelves i would quickly have them filled. if that step down gives a problem i think the least expensive solution is a slanted piece of wood shoved against it. well and glued down. if you ever want a little more color or zip, let me know can give you at the least some cool pillowsl. let me know.

Move round table toward wall for now so you have a pathway to slider door. Not sure what the person you had helping was thinking but we ALWAYS map out walkways and “transportation” around and between rooms. The basic furniture is too large for your space but this is probably best arrangement for now. At some point, I would put chairs in a media room or game room. Two smaller scale swivel chairs in a complimentary fabric would improve everything. A “gate leg” table behind sofa would serve dual purpose. When leaf is raised 3 could eat a meal. When lowered it would act as a sofa table.

The current TV placement is the best spot, but it should be lowered to proper viewing height. You should be able to fit a sofa, maybe not two chairs depending on how big they are but they can flank the fireplace.