1.)Depends how many, 3-4 in a 75 or a small colony in 100+
2.)I keep and breed mine in a rather assorted mbuna/hap community.. From experience they only get nasty around breeding time. Even then they don't actually "attack" other fish, they just herd them away from the breeding pit.
Having said that, a 15cm dimi comp will quickly back down when a 6cm Acei challenges his authoritaaah!! (very funny sight actually)
Just for the record, my community as includes fish that are big enough for them to eat, so their hunting instinct can be "grown out of them"
3.) Can't help you, i'm in Aus sorry.
4.)The more the merrier, this is a general aquaria type question, they're not overly messy and will finish most meals. I hand feed mine so I know they will get their fair share and not spit any out.
Few more points:
The fry are very touchy. Keep pristine water conditions and feed little amounts regularly..
If you don't you could lose the entire herd of fry within hours.
Never underestimate their intelligence, if they want to get into a tight or unreachable spot, they will. IE. fry nets
I have only ever experienced "eye biting" amongst there own kind. Even then it could not be 100% proven so I have my doubts of this name.
When you find some, love them and appreciate them.
They will reward you with countless spawns, and will grow to appreciate you in return.