> Should I look to getting him neutered now to keep his temprement easy-going?
NO!
>He is also going through a fear stage
This is exaclty why you should not consider neutering him now, any confidence he gets from his dangly bits will be gone and he will be more likely to be trapped in a fearfull state.
> my mouth was full and he was stealing food so I mumbled a 'No' which sounded more like me growling, but his re-action was to raise his hackles
hackles are not a sign of agression, they are a sign of
arousal, fear, ecxitement, uncertainty are all things that are 'arousing' and can trigger the hackles going up, it's best to think of them as being a sign of 'tension' than anything else. He may well of felt threatened by your 'growl' and his hackles rose, but that doesn't mean he reacted agressively
> The male he has taken adversion to is a 6 mth old spaniel who is no threat at all.
Is this the only dog he has problems with? It may be a case that he simply does not like the dog.
Buster met his bestest friend in the whole-wide-world yesterday, an entire, male rottie (Buster is entire too). They recognised each other from a fair distance (both on lead), and when they finally got face-to-face they exploded into a greeting frenzy, like long-lost soul-mates :-) Another leashed dog was approaching, it was growling. Apparently the rottie does not get on with that particualr dog, and as it got closer the rottie was straining at it's lead, growling & posturing, so was the other dog. If they had been loose they definatley would have had a punch-up :( When the other dog had passed us, the rottie went back to being a big, soppy baby with Buster and we carried onthe walk together. Apparently there are about 3 dogs the rottie does not get on with, every other dog he loves to bits. Some dogs simply do not get on with some particualr dogs, but I doubt it's a testicle thing, it's a personality clash - even neutered dogs can take a dislike to another dog.
I'm sure somebody with more experience will give you some advice as how best to manage your pushy teenager, but I think most will agree - the dangly bits are best left in place untill the dog has also
mentally matured into adulthood.