Before doing all this - its better to install the speakers in the room where they sound the best, with less boomy bass.You are struggling with Room Modes, which will cause significant dips (up to -20dB) and peaks (up to +20dB) in your signal below ca 250Hz. The peaks cause resonances and that boomy sound. We all experience it. Good news the peaks can be dealt with. The dips only by adding several subs.
There are many ways how to approach this, but the best solutions involve some sort of digital Room EQ and frequency response measurements. Doing it manually, like you, takes a lot of experience, a lot of time and still has no guarantee of success.
Get an AVR eg with Audyssey or Dirac and let the automated system do it’s job. The boomy bass (room resonances) will be addressed with this already. This needs the LFE channel.
Get a UMIK1 measurement mic and REW (free) to measure the frequency response yourself and enter the calculated EQ filters in a Software EQ eg APO EQ, Moode etc of your choosing.
As described in „more advanced“, in addition get a DSP eg MiniDSP to do the EQ filtering , plus up to 3 additional subs and optimize the bass distribution in your room by using the MSO software (free).