Ditch the bob before he injures one of the hens. The bob bird is a contentious subject (whether it even exist is still argued), but basically it is said to only work the one way. The other cross produces no fertile eggs at all as I understand it. They couldn't be more unrelated though and it's amazing that the cross works in either direction. They aren't even in the same biological family. Most of the cool hybrids you see involve birds from the same family, such as the chicken pheasant or the various other pheasant hybrids out there.
It's not a good idea to keep multiple quail species in the same cage at any rate. Especially with an aggressive species like bobs with a docile species like coturnix. Coturnix roosters are usually pretty easy to come by since the eggs hatch pretty much half roosters and you only need one rooster to cover 3-7 hens. Most people have extras, you just have to find someone who doesn't eat their extras before you can get one. Worst case you'll have infertile eggs for a while til you find one.
When you get a new rooster make sure to integrate the birds by first putting their cages near each other in full view for a couple of weeks. Then move all of the birds to a cage they haven't been in before. After you put them together and establish that they are getting along (mating looks a little rough but you should be able to distinguish it from outright aggression) then you can move them to whatever cage you'd like. Quail are really territorial and will kill each other over territory so take the integration process seriously.
