It seems to me -

• Michael's safety on his return from Sicily was brought up by Vito only after the above peace agreement was reached

Whilst Vito's veiled threat, should anything happen to Michael “And that, I do not forgive” in reality there was little to nothing that Vito could have done, in the Corleones' dilapidated state

• Philip Tattaglia and Vito Corleone [agreeing] to forgo any individual vendetta” sure thing “would be binding on their respective Families too”

However any other action eg: "horning in on” other Dons' territories whilst not the act of a friend! is outside this agreement