No.The 560R and 220nF are supposed to be a low pass filter at 1.3KHz.
It has the fairly low 560 ohms resistor in series with the same output impedance of the PIC so the cutoff frequency is about 649Hz.
No.The 100R and 20R are a voltage divider to take the 5V peak to peak signal down to 1V for my stereo line in socket
The 100 plus 20 ohm resistors load down the output of the filter so it doesn't filter anymore. they also load down the 560 ohm resistor and also load down the output from the PIC. The output of the 20 ohm resistor will be about 0.069V peak which is too low for a line output.
Your problem is that your resistor values are so low that they need the very low output impedance of an opamp to drive them. But many opamps also cannot drive resistor values so low.
The Pic should drive a load of at least 5k ohms, not just 680 ohms.
The filter should feed a load of at least 10k, not just 120 ohms.