I'll put in another vote for Room EQ Wizard software, which is free. Spend some time on the tutorial videos. It takes a bit of time to feel like you are even a novice, but this is a hobby, right?
While I'm at it, I would take a vote away from GIK acoustics. I've heard nothing but good things about them, but my own experience was disappointing. I had the strong impression that they wanted to convince me my room had the problems they could readily solve rather than the problem I wanted to fix. I eventually worked with Music City Accoustics and had excellent service with custom work done with amazing results.
But back to the software...both of these companies will want your data files generated from REW, and so taking some measurement first is definitely the right thing to do, especially given the weirdness of your room.