I have a male and female eclectus, though both are young and fairly close in age. (2 years and 1.5) But to keep them from breeding, I can tell you the basics. Separate cages, of course. No nest boxes, nor anything that might be used or construed as nesting material. No closed off, dark places that might even slightly resemble a nesting hollow. If, in addition to all this, their out and about time is supervised, then you'd probably never have a breeding situation.
Sure. Just far enough away that one couldn't reach the bars of the other with an outstretched foot. (More of a safety precaution than anything else. Don't want any missing toes if one or the other is in a less than charitable mood.