Will stone us (katalithasei). Late verb and here only in the N.T. Literally, will throw stones down on us, stone us down, overwhelm us with stones.
They be persuaded (pepeismenos estin). Periphrastic perfect passive indicative of peithō, to persuade, a settled state of persuasion, “is persuaded” (no reason for use of “be” here).
That John was a prophet (Iōanēn prophētēn einai). Accusative and infinitive in indirect assertion.