you can only have one because that is a special item granted to a player who completed the Moscow special event 8 items.
joining a clan or family, or by posting to one of the many different sites that are mafia wars add sites. Depending on where you play, you can just type mafia wars into the search site, and many different things should come up.
You can only have a maximum of 501 and many people have that.
so far there is no limit on how many family you can have on your mafia family but you can only take 500 mafia families to attack.
3
320
As high as you can practically go
As of now, there is no known limit.
This was a special loot that randomly came up and offered in Mafia wars. Like the gas mask and now they are offering the meat cleaver. The amount of mafia members you have decides how many of these you can get. You can also now get this item by buying a mafia crate.
Unlimited, or as long as YOU can go i guess you can say.
4, as of 6-30-09.
Just one of each collection.
There are many glitches in Mafia Wars (as with any game, be it console or javascript based) If you google MAFIA WARS and GLITCH then plenty will come up; some even on youtube. You have to be quick, though, as many are fixed very quickly. The free godfather points ones seem to be active still (march 2010)