Splitting Audio Out - are there any issues I am not seeing?
The 1k series resistors are needed if you are summing any of the chip outputs together.  This isolates each output from the others.

You can add 3- additional mono outputs if you wish: connect another set of 3- 1k resistors between each output jack and the chip pin.

If you want a total of 4 jacks: 3- mono signals plus a mono sum of all of the signals, do the 3- individual jacks as I have described above.  Then connect 3- separate isolation resistors from the mono sum jack to the chip output pins.  Ideally, these 3 resistors will be about 3k3 in value rather than the 1k you are using for the individual signal jacks.  The higher-value resistors provide greater isolation (minimize cross-coupling of the individual outputs).  

The combined mono-sum output still has a similar output impedance to the individual output jacks (1k vs 1k1).