I shall direct you towards the thread right on the front page of tactics, regarding Ork Bikers covering most of what you're asking:
http://www.dakkadakka.com/dakkaforum/posts/list/492856.page
Remember to check before you start threads
To answer your questions while I'm here:
Yes
No
Yes
No - two
PK's usually, 3 *very* rarely, if ever. Remember to keep them cheap. Put non-
PK's up front.
Remember, they are toughness 5, with two wounds, a 4+ save, and a constant 4+ cover save. And then toss a 5++ and
FnP. They are very hard to kill. 6 is enough, many run them as just 5.
Warbanner is mandatory.
You CAN put a bikerboss in there, but it's not required. They kill lots as it is.
If you do put a 'boss with them, you've got it pretty much how others run him (though the
BP is optional, as the nobs can buy it).