Breadboarding digital mixer: deriving Vref from Vdda, and capacitor between Vdda and Vssa?
1) How to get .44 of Vdda - A voltage divider and or suggestions?


Yes, a voltage divider should do fine.  It'll be to set the virtual ground point of the op-amps, and when using discrete op-amps I use a voltage divider for just that reason.  It'll be 0.44 because the op-amps may not be rail-to-rail, so shift it down slightly to the mid point of the active available region.


  2) Is the schematic correct in that I place 1000pf capacitor across Vdda and Vssa?


Yes, that is correct. Basic decoupling capacitor.  You can add others too, maybe 100nF and 1µF.  You should add some decoupling to the Vddd/Vssd as well.


  3) One of the comments for this IC / digital mixer chip is that I should keep all analog ground contacts separate from any digital ground contacts?
  
  Does that imply that I keep the analog and digital power supplies separate as well?


No. You should still connect both grounds together, but do so only at one point, and maybe with a small ferrite bead between them.  Both power supplies can be the same power supply (and should both be 5V anyway), but again you can separate the Vddd and Vdda with a ferrite bead.