Guys, I have some bad news. I think we aren't getting this yet, sorry.
First of all, thank you to all of you for trying to help of course! I'm not giving up and I still hope that we can make it.
fieldcar, in your latest repair (spectralayers manual 2), you didn't erase the hum at all. You got rid of some bass line that's necessary to the song, which makes it of course worse. Sorry to say this. On the bright side, you were right to say that it was intentional - because it is !
The hum is not there.
I've tried to locate the hum once again with IZotope RX, and using the time-frequency selection tool I think I've managed to isolate it somehow. It seems to be located between 4250 and 4750 Hz
(at least I hope it's the hum itself and not one of its harmonics). And remember, it's located only (or mainly) in the right channel.
RX allows to create a new file with only those selected frequencies, so here it is, in the most critical part of the song (0:36-0:40).
For the record I can hear it perfectly with headphones and with either RX or foobar2000, but I can hardly hear it with Audacity. Go figure.
Can you guys hear it now? And
@Jimbob54 , is that the hum you are hearing too?