I think that if this boy was neutered more than a couple weeks ago, he ought to transition fairly easily. Inside of that period after neutering there can still be enough hormones there to cause isssue. It is not just the spraying but the unpredictable aggression. For some reason the male hormones have a stronger effect on male cats than male dogs... male cats under the influence of hormones, if they feel uncertain or threatened in any way can go from cuddly kitty to scary kitty FAST.
Aside from the hormone thing, once past that I've always found as Pam has that the males have stopped spraying and that they settle to being big lovebugs. I've always preferred homing my retired males either as only cats or with one other female cat...just to keep things easy in that transition. Mine were all raised as pets before their breeding time, so seem to revert to that life very easily. As long as this male has lived a pet life in his early days (until he started spraying and breeding) then it should be an easy thing, if he's always been in a cage then it might take longer to win him over...but when his only company is YOU, then he is motivated to get to know you eventually
Aside from the hormone thing, once past that I've always found as Pam has that the males have stopped spraying and that they settle to being big lovebugs. I've always preferred homing my retired males either as only cats or with one other female cat...just to keep things easy in that transition. Mine were all raised as pets before their breeding time, so seem to revert to that life very easily. As long as this male has lived a pet life in his early days (until he started spraying and breeding) then it should be an easy thing, if he's always been in a cage then it might take longer to win him over...but when his only company is YOU, then he is motivated to get to know you eventually