I don't understand "Traveler is not Level. It is also dead. Halo rings affect everything period. All Living life is gone.". Flood would be stopped by Taken who are basically spirits so they can't be infected. Hive Gods would have enough Halo universe "scum" to feed off of. Flood couldn't take down the Gods unless they were at their full power, but they wouldn't be because they would be taken care of before they could get to that point. The reason I wouldn't have the Flood at their strongest immediately is because every battle they've been a part of they started from a small group.