Reading the old posts, I see a previous poster and I arrived to the same solution, I added 680ohm in parallel with those 470ohm on the solder side, lowering the resistance to 277 ohm. So in both cases replacing 470 ohm with approx 270 ohm lowered the DC offset. You can add a resistor on the solder side as I did. The effect is the same than replacing the original resistors.
A small offset won't damage your speakers, headphones or amp. Some amps are working with 100mV DC at the output. The ideal value is zero, so getting closer to zero would be better. But if you'll be risking the amp, a working amp with 90mV at the output is way better than a blown amp.
I see, that makes sense. I think Im going to order the resistors, but Ill use the amp as is in the meantime, and keep it in the back of my mind that I need to fix that. The method that you did seems fairly simple so hopefully that works out when I eventually get around to doing it! I thank you so much for your help, you spared me the pain of going back and rereading old threads on this stuff.