I have just now heard about that and it seams that its almost always the Natural Choice. But you can find lots of bad things and good things about every brand of dog food and it hard to pin point weather or not it was the acctual foods fault or a plant mistake or maybe the stores falt, it could have been molded or the bag could have had something spilled on it, the bowl the dog ate out of could have had something to do with it. More and more people now a days are blaming it on the food they feed and pointing fingers. The first story on the link you posted said the lady had been feeding the food for a week, any food changes should take more then that amount of time to switch and what did the dog eat before that happened? Was there rat poison around? Did it lick a frog? Many things come into play and you have to take everything with a grain of salt.
If you feel uncomfortable switching foods then by all mean don't do it. I have never had a problem and any problems my dogs have had were from outside sources. Cher, (she is my problem child) likes to eat cat poop and becomes very sick, lethargic, wont eat anything, bloody stool and vomits.
On to the neutering thing, if it were me (I would have him fixed
) I would ask myself why would I want to breed my dog? If he was bred would he be contributing something positive to the breed and its standard of perfection? What you said here -> We haven't really looked into it, does it affect the way they act around other dogs other than aggression? <- Would suggest you no breed him and look into what owning an altered male dog consists of.
Unaltered male dogs can and will have same gender aggression, they can have dominance issues, become possessive of toys or even you and your home. They will seek out females in season and there is not a lot you can do to stop him and many male dogs will become aggressive around bitches in season. I know an unaltered Poodle dog who will stave him self for weeks if there is a bitch in season any where in a 5 mile radius and will whine and howl for days. The owners are having him neutered this month.
Anyhoo I have to go but I'll be back because I have more to say!
Good luck with him!