deeve, you're on the right path.
observation and close attention will let you pinpoint what is the set-off for Micaud is. maybe he gets startled? if he is sleeping and suddenly someone screams or yelps..?
the cat on the roof, could it have come to visit your stairway? then it would have set off your kitty, as theres an intruder on his territory..
also, I am worried that Micaud could one day take off and go exploring, up or down... or chase the other kitty... be careful about that! is he leashed when outside? if yes, another concern to make sure he doesnt hang himself on it..like if a bird lands on the railing and he jumps for it, that sort of thing.
Good luck for the 22nd, I hope he gets snipped then!
Another little thing
: I have a 3 month old kitten, she plays rough with the dog. I always watch them and as soon as she gets too much into it - I separate them. Sometimes she is so much into it she redirects to me, starts scratching and biting. I lift her by the back of her neck and dont allow her to do that, but once or twice she was so agitated I had to put her in her room (bathroom) for 15 minutes cool-off time.
I noticed a change though, it works, when I say "no biting, gently!" now, she lets go of the dog and backs off. Now, she is 3 months old, imagine when she's fully grown? she will be fully capable of drawing blood so easily!
I really hope its just a hormonal thing, but you need to keep the puppy and the kitty apart for now. then, reintroduce them with supervision.