"Led astray with them" is a metaphor, as if Barnabas was following on the correct path but then became deceived and started going on the wrong path. AT: "Even Barnabas was deceived along with them."
This rhetorical question is a rebuke and can be translated as a statement. The word "you" is singular and refers to Peter. AT: "you are wrong to force the Gentiles to live like Jews." (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-you]])