I cannot really comment on the realities of the war and whether or not it is accurately portrayed. But, I will say that anything can happen during one of these things! It only takes one soldier/associate to betray his family or someone within his family and we end up with a Masseria, Maranzano or Anastasia.

Phil wanted to kill Tony, Bobby and Sil certainly, but I don't think he had any other targets in mind. Once he got them out of the way he was going to do business with what was left, so it might not be called strictly a "all-out" war, but yeah it could go either way, especially if one or more of the other 5 families were to side with either Tony or Phil.

That's an interesting question about Butch and Albie. Butch never hid his animosity for Tony in the past, and Tony couldn't have known that Butch was unhappy with Phil.