You can play around with toe-in to compensate but you will probably always hear that un-even response. You need to re-model. Add a pocket door, or take the whole wall down and reconfigure which is what I did years ago. I had two big openings, one into a dining/kitchen area and one into an entry foyer and no room treatment or placement could compensate for that. I put up new walls with french doors that are beautiful to look at and let all the light from the other rooms come through. It is a decision I will never regret.