I've never fasted while doing the oxypowder cleanse, so I don't know if that would be more beneficial. Have you done the cleanse twice? once while eating food and once without? How did you feel with each? Here is the official page for Oxypowder's 7-Day Intestinal Cleanse. It actually says to avoid juice, unless the label says it's 100% juice. So, it may be best to call the oxypowder company and see what they say.
How many BM's did you have the first day? If you had 3, I would consider that the first day. But if you feel like you could use an extra day or two on the cleanse, there is nothing wrong with continuing on with the cleanse after the initial 7-day period. I usually go beyond the 7 day period myself. And I've always felt great afterwards.