1. truly dont know
2. schools are ideal for management traits, tremendously useful, but dont build them in every city. one is enough, when your character gets bunch of great traits, get him to another city instead of building a school.
3. Move your capital to mediolanum, that should keep them happy for a while, but when Capua, e.g., reaches 24000 population, you have one choice: let it rebel, enter it and exterminate. And if you are in italy, go across the adriatic and take dalminion and segestica, mines will give you around 5000mnai per turn or something like that
4. hold alt and double click and turn fire at will, btw
5. first of all, what do you consider a good general? the most important thing are morale traits which you generaly get by charging relentlessly and keeping him in a fight. With a good general that gives you +5, +6 morale, you can have a cheap army that kicks ass. And yes, some tribes have better chances of acquiring such traits, as you said, belgae and such. Caturiges are ok...