Thank you Michael and Sanjay.
Please bear with me, I am trying to understand the concepts and also I believe I do some measurements mistakes while performing the tests. I am attaching several photos/screenshots to give a better view of the room and also new measurements as you suggested.
First of all, perhaps it's time to ask couple of preliminary questions I had:
1) Why windows audio/ rew don't differentiate the surround (rear) speakers from top middle speakers (5.1.2 atmos setup)? My connection is OK via HDMI, can hear sound when selected Multi-in and Atmos displays on the receiver when I play netflix atmos content or dolby access demo. But in the speaker configuration (windows audio) and in REW when I test the top middle speakers sound is coming from rear surround speakers (the content plays OK just the speaker test/rew doesnt send signal to top middle speakers)
2) Sometimes in REW back to back measurements is giving different results (attachment 02 and 05 is supposed to be same but the dip at 80hz isn't). Perhaps I mix up things or perhaps it is the crossover point.
Now, for the measurements I am attaching below results for:
09_sub_R+L_phase_0-0_-30cmfromMLP.jpg - - - - I conducted this measurement afterwards and I don't know why the SPL is so different (I believe I did this after setting up the limiter in the DSP)
And in my next post (due to number of attachments) I am posting some photos of the room and its size along with the setup info.
Finally, I believe I forgot to put a limiter in the first 8 screenshots hence the high dB figures. OK it was loud/rumbling at 40hz but I am not sure whether it was around 120dB (I thought it should be much louder).