QuNexus spits out CV, 0 to 5 volts — there's nothing special about it.
One, after you changed the preset to put velocity on CV 3, did you save and send the preset down to the QuNexus using the big "Save & Send" button? The QuNexus doesn't automatically update itself, you have to explicitly send presets down to the board.
Two, are you using the correct preset (the one you changed)?
Three, what kind of cable are you using with the CV out? The CV outputs are TRS (stereo) connectors, so if you're using a TS (mono) cable then things may not work right. A simple stereo 3.5mm (1/8inch) to dual mono cable works nice for the CV outs.
Four, if all of the previous things are correct, did you plug in the correct CV out? If you're using a stereo to dual mono cable it can be hard to tell which cable corresponds to which CV out.
Five, what voltage range does your modular respond to? QuNexus outputs 0-5V.
To turn off the bend pad (except for CV):
1. Open the editor
2. Switch to the controller layer tab
3. Click on the bend pad
4. Uncheck "Participate in Keyboard Layer" (and "Participate in Controller Layer" if it happens to be on)
5. Save & Send the preset
2, 3, 5, 13, 89, 233, 1597, 28657, 514229, 433494437, 2971215073