When doing corrections with REW, it is best to get started with some smoothing. like 1/96 octave to 1/32 octave. Without smoothing REW will try to correct things that depend on your listening/head position.
I usually do multiple measurements with slightly different microphone positions around the listening place. Then create an average sum of these, and smooth with suitable smoothing level, before applying correction.
At low frequencies the corrections can be more drastic without adverse effects (just don’t try to fill dips more than about 6 dB). But above 500 Hz or so, only gentle corrections are fine. Otherwise the corrections will likely sound pretty strange if not disturbing or irritating.