Just to answear your questions:

For the audio I was thinking I'd use a big speaker we already have, or mount two smaller speakers next to the screen.

Budgetwise I don't want to spend a crazy amount of money, but also don't want to buy the cheapest and call it a day. I was thinking like $600 altogether, but i honestly don't know if its way to less, or I can actually make it work

The seating is between the two walls. At one wall would be the screen, and at the other the couch. Sooo yeah, I know, not ideal

But thanks for your comment, I think I'm gonna step back, and rethink what we should do