I agree with you that Abir's blind spot is Kunal. So while Abir's way of questioning may not have been ideal, it explains why he did so. At that moment, Abir's priorities were divided between Mishti and his need for stopping any more issues that can affect KuKu wedding. So he decided to take the middle ground by asking that painful question to sort out matters in front of everyone. If only KuKu weren't hell-bent on wrecking things... but oh well.
Anyways, I liked the part where Mishti goes into attack-mode at the person who mentioned about her email id. And the precap gives hope.