This is the correct approach. Your rack expects 1 volt per octave. You now now that your interface acan provide about -3 to 3 volts DC. The output appears fairly linear so you should be in good shape. Your maximum swing is about 6 volts but that translates to 6 octaves which should be pretty good. You will probably need to tune your oscillators up an octave or so if you want to use the full range.
Given that Audulus expects 1 per octave and your interface gives you about 3 octaves from 0 to 1 you will need to divide the Audulus output by 3 or so to get reasonable pitch tracking.
You might find this useful: ES-8 interface module download