Can someone explain the drop rate details of the keys to rubies conversion process? It seems like I was getting more rubies before the nerf patch...sometimes now I burn a full day's worth of keys and I get no rubies at all. Was the conversion rate nerfed? Is it random and have I just hit a patch of bad luck? Also, it seems unlikely, but devs in other games have been known to do weird shit...is there an advantage to using keys all at once or individually?

Unrelated, but is 99 the max chair level?