Going by Rudra's adamancy to accept how genuine and strong Paro's feeling for him are and his dumbstruck expression at whenever he speaks so fondly of him it is very clear he is so overwhelmed by her love for him, it's probably the first time someone has seen him in this light and has really wanted him, the way he is with all his flaws.
Everyone sees him almost a beast, Laila with whom he shared a sort of relationship has called him "janvar" more than once, his own dad tells him how bitter he is but Paro accepts his aggression and anger and even compares it to Shiva.
So far Rudra has been abandoned by his mother, his father hasn't really been affectionate while bringing Rudra up, KCM never showed him love, just taunts, he's never formed friends because everyone would just taunt him about his mother but Paro wants him, the way he is, with all his shortcomings.
She sees right through his anger and sees the love and care in his eyes
She sees the protectiveness he feels for her through his selfless acts to protect her
She sees that whatever wounds and bitterness he gives her now is all better than the life she would have had, had he let her cross the border
And by acknowledging all this out loud in front of Rudra she's done something no one has, she's valued the presence of Rudra in her life, she's assured him that she wants him for a lifetime (by believing so deeply in their jugaad ki shaadi)...for a man who has faced rejection, abandonment and misunderstanding all his life it's hard to take in how much she actually loves him
Along with that I think he is also overwhelmed by how much and how deep he can feel for her if he actually accepts his feelings, he already goes "bawala" when she is hurt or in any kind of pain or discomfort.