To use the XA with off camera flash use an optical slave & PC cord.
Small auto flash for the remote, PC cord with optical slave plugged in to the sync end(really?) and tape the slave to the flash for the XA.
Make sure to cover the entire of the flash tube with an opaque tape so you don't have any light leakage. A11 would work fine.
Want softer light? put a layer of lens tissue or two over the remote flash.
I could modify an A11 (I have bad A11) and pull all the guts out put a PC connector on it. Still with the XA to lock the shutter speed at 1/30 you have to move the aperture setting to flash which is fixed at f/3.5. Setting the aperture any where I want the flash still fires but the shutter speed will automatically goes slow when use flash in a dark place.
What Chan said, The ttl cord for the Nikon would need the four contacts both on the camera and flash.
In your case, you have them on the flash but not the camera.
That said, the ttl cord would trip the flash but would not give you ttl(through the lens) control.