Huge bummer man, I had the same thing happen to me on this grow. It also had Headband genetics... Headband X Plushberry. It showed female pre-flowers right before I put it into 12/12 then at about a week it was clearly a full blown male. Some plants will do this, it doesn't necessarily mean they are hermies. It can also go the other way, pre-flowers looking male initially then you get a female with no hermie traits.
I think you have a full blown male there, unless you see any pistils... If it is a solid male you might want to keep some of those sacks, let them open, dry out the pollen in a dark place, then mix it with some flour put it in an air tight container and store it in the fridge. Make some Headband X Blackwater. Personally, I wouldn't keep any pollen if it is a hermie.
Very nice job on this grow BTW, regardless of your bad luck.