When I took florence, my rep didn't change. It has been mixed since the start of the game, it still is. I occupied Florence and kept a fairly large force there, about half a stack.
Sicily was the first to attack me(Genoa), for some reason they did this with a rediculously small force. I sallied against them, defeated them and released any prisoners since I'm going for the chivalrous path here. they didn't withdraw their army but kept it standing next to Genoa. After this they asked for a cease fire, which I honoured. Army stays put.
After this everything seems fine and I take Ajaccio with a single general(Occupy). I made my alliance with spain and a trade agreement with france. I did this in accordance with the OP which says both of those factions are doves, but an alliance with france is too risky. Rep is still mixed.
Now I Occupy Cagliari with some militia (5 units or so). Rep is still mixed. But after this all hell breaks loose. Suddenly there's a Moorish and Byz army next to Cagliari and just a Moorish one near Genoa. A Moorish diplomat asks for trade rights, which I decline since their motives clearly aren't peacefull. The moorish army near Cagliari attacks, I defeat them and fend of the army near Genoa (I attack, they withdraw) after which I ask for a cease fire which they agree on.
Next things that happens is that a Venetian diplomat demands I become their vassal (not a chance), I decline and they attack with a small force (Milan). I defeat them but the next turn the diplomat repeats his demand, which I decline again after which a full stack including their king attacks Milan!!
This is where I am now.. I've tried to defend against that army twice now but I'm having great difficulty with an extremely annoying bug where my framerate drops to about half a frame per sec. after I have set the game speed to 6x and back to 1x... Happened both times and I had to kill the game via task manager. I guess I have to try again without touching the game speed button. I've never had this before and it sucks!!
Edit: Some screens.
After seeing these again I think there might be some chronologic errors in my story, as it seems the moors attacked between the two venetian attacks.
I'm afraid my campaign is looking quite hopeless allready