Aggression

We have a year and a half old English Bulldog Hercules, he is not fixed, I think this may be part of the problem, but my husband refuses to fix him. He is very aggressive to all other dogs and tries to attack any dog he comes into contact with. However he has been raised around our female beagle mix and loves her. My husband and I are both deploying in a few months and we have tried everything to get him socialized. My parents who will be watching my kids and pets has 2 English Mastiffs, and my fear is that although they are not aggressive, Hercules may attempt to attack them and he would get seriously injured. Does anyone have any ideas? I have not found any muzzles that would fit him in any of the pet stores and I dont know what to do at this point. He is great with cats, and kids and people but other dogs he becomes a totally different dog and I am very scared, for his safety and other dogs safety as well.Please help