The best I can do is refer to the mere beginning of this board and the "More bass" and such topics (two of them exist). There I let "you" the customers change things in the DSP itself - already quite a task. Turning this upside down : if you can't perform that, then all stops, because it is part of the job.
The (indeed) REW part is something you can learn, but it requires a measurement microphone and an A/D converter to get from the microphone to the digital data in REW.
The measuring itself ? a job which requires a lot of experience. But what you always can do is measure the base (as how all outputs currently) and gradually change things (in the DSP) which you *and* will see happening *and* will hear happening.
See you in a year ?

(not talking physical visits

Best regards,
Peter