Does obsessive whispering prevent the one afflicted by it from clarifying the most correct view on a specific issue to others? And what is the ruling on praying behind an imam who does not adhere to the correct prophetic ablution?

Being afflicted with waswasah (obsessive whispering/doubts) does not prevent one from seeking knowledge, disseminating it, engaging in scholarly discussions, and clarifying the strongest opinion with its evidence. Your previous prayers behind the imam were valid if his wiping over his feet was hidden from you, because any invalidator that is hidden from the ma'mum (follower) does not affect the ma'mum's prayer. However, if you know that he wipes over his feet and does not wash them, then do not pray behind him in the future because his prayer is invalid. You should also advise the congregants and inform them of this so they can replace him.