A few things to consider:
The main echoes you hear are whats called "flutter echo" and happens between to hard boundaries that are parallel (in other words, parallel walls). For example, your floor and your ceiling are not parallel, and even if they were, there is carpet on the floor so your flutter echo will only be due to your side walls and not the ceiling or floor. So for maximum difference for the cost, you should just stick to wall treatment. I usually recommend treating the first reflection points in the room and the rear wall. Rear wall are typically has a lot of bass buildup so thick treatments (6" or thicker) work pretty well on the back wall. Reflection point panels can be 3" or more. If you do surrounds, treating the front wall can help keep the surrounds from blending in with your front channels (so the surround is more "surround" and the mains are more directional")
I would position your couch so that it is in front of the TV/speakers instead of to the side, and try not to sit directly in the middle of the room. A few feet forward or back from the center would be your best bet (judging from the photos, about 3 or so feet from center). The TV and speakers should be centered along that wall.
You don't need to take measurements unless there is a specific problem you are trying to quantify and need to address.
For an example of a treated theater room for under $1,000 - consider a set up like this:
Obviously, this is a more idealized single-purpose room, but the general ideas can still be followed. You could do traps in the rear corners like this, or focus more treatment on the back wall with flat panels instead of the corners.
