Sorry i didnt get to your question sooner, i just havent been on much lately..
Glad you have found some knowledge through my posts! Overall i dont have a lot of experience with ebb and Flow so i cant 100% tell you for sure... But you shouldnt ever need to run just h202 and water during the flower... other then the flush that is... Which i REALLY recommend you make sure to flush with RO/h202 for the last week of your grow, it will help to use up all the nutrients stored within the plant... But yeah other then that your reservoir should have nutrients/water/h202 for all but the last week of your grow...
Also, not sure if you know but i really recommend the 48 hours of darkness before chop to, i know we have all heard it argued but overall im a believer that it really does help to stress the buds into one final plumping.
have a good day man!