I think I would have been surprised if he just accepted her easily after all that has happened. So his reaction did not surprise me. He is just a normal human & like every normal human being he is trying to shield himself from further pain. Self preservation is not cowardice or self pity.
Also, he does not owe it to Swara to accept her with open arms as soon as she confesses her love. She took her own sweet time understanding his love. So instead of dismissing his rejection as "zidd" she should accept it & double her efforts.
He is a go getter no doubt. He proved it when right after she said "they blessed me with a happy married life" making it sound that she considers it more a curse than a blessing, he told her exactly how he felt...mat todo ye shaadi, bann jao meri patni, etc. Because then he still had some confidence in their relation. Later on he even went so far as to flirt with her when he saw her thawing. But then she broke the one thing which held them together i.e. trust. Going after her after this would make him shameless in my eyes. He is a strategist but he might just be done trying here. If he was truly a weakling he would accept whatever scraps she threw his way & be happy that she finally is in love with him, reasons be damned. But he has played the convenient puppet long enough & this time he will accept her only on his terms. He chose to have it all from her or nothing at all. That needs real strength.