Found a good method of bass boosting songs. However, with some songs, the original song has more of the sub-bass frequencies, and the other bass frequencies are inaudible to my speaker (response of 65 hZ to 20 kHz), but not my headphones.
I'm not sure what you're trying to say or what you're trying to do...
As a general rule, it's a bad idea to change the recording to match the playback system. If you want to EQ for your speakers or headphones, that's best done at playback time. But if you want to do it, you'll probably have to make different copies for your headphones & speakers, plus you'll probably want to keep a copy of the original in case you want to play it on a better system.
Also,
you shouldn't be making drastic EQ changes unless you have drastic problems.
but still leaves the part of the song I want to make audible inaudible to my speakers and headphones.
It's a loosing battle trying to boost frequencies (especially bass) that your speakers can't reproduce. For example, +3dB requires double the power (Watts) and +12dB is 16 times the power. Bass already takes lots of power, so you need a big amplifier and if you don't drive the amplifier into distortion you end-up driving the speaker into distortion or burning-out the speaker.*
Deep bass is more felt in your body than heard with your ears so you don't experience bass the same with headphones although you may feel the headphones vibrate on your head. (But of course, you need big woofers/subwoofers and big amplifiers to feel deep-powerful bass in your body.)
I also understand frequencies can mess with others. Is there a chart for that? For example, boosting 240 hZ lowers the volume of 80 hZ (I don't know if that's actually true or not, just an example).
No, that's not true... But that can happen indirectly... If you boost some frequencies and then lower the overall volume (with the Amplify or Normalize effects, etc.) to prevent clipping you can end-up with a quieter-overall recording, especially if you're boosting frequencies that you can't hear or frequencies that are hard to reproduce (like deep bass).
* The same thing happens when you try to equalize for room acoustics. Standing wave antinodes (where the soundwaves increase the volume) can usually be fixed by cutting with EQ. But, at nodes where waves cancel at certain frequencies it can take an almost infinite amount of power and infinitely huge subwoofers... So EQ doesn't work and you have to treat the room acoustically with bass traps, etc.