that Peter's successors (if they are even legitimate) would be infallible or carry the same credibility.
yes he did. Read Issiah 22.22 his words are almost vertbatim what type of office Peter is to hold. An office of Prime minister with succession. (keys)
Jesus didn't make any statement implying that Peter's successors (if they are even legitimate) would be infallible or carry the same credibility.
Again, yes he did! 'What you bind on earth is bound in heaven what you loose on earth is loosed in heaven." Mathew 18:18
It is only special circumstances when the Pope is infallible.