I assume that the seven bands (63Hz, 160Hz, 400Hz, 1kHz,
2,5kHz, 6,25kHz und 16kHz) mean "0Hz-63Hz", "0Hz-160Hz", ... and not "0Hz-63Hz", "63Hz-160Hz", ..., right?
No wrong on both counts it is a band centered on the frequency mentioned. It is only a low order filter so these bands might overlap for loud inputs.
I would like to use 3 x 68k (=204k + tolerances). I guess that this is o.k. for a qualitative peak-meter!?
That will be fine.
The resistor on the audio in is to stop the left and right channel shorting out. If you have a mono input you have no need for it.