Disclaimer: These are only my thoughts from how I understood the characters. I could be wrong. My experiences with life and people around me could have influenced my understanding too. :)
I wanted to write about Virat's behavior for quite sometime now but was not sure how to convey his situation. He is definitely in a 'tricky' situation for a good man like him, who thinks about all the possible outcomes and about everyone. This situation could have been so simple for Sai kind of a person, who is also good but impulsive and straightforward. So to first understand the behavior of Virat in dealing this situation with Pakhi and Sai, we have to ponder on his personality and the circumstances he is in.
I know sometimes CVs dont give us good dialogues and the character arc so we get confused at character's behavior. We have a good actor like Neil who conveys some of the complications/deliberations that Virat's character faces. If we can observe them closely, may be we get some answers. But as an actor he can do only so much. Anyways, let me put down my thoughts on his behavior. Lets see where Virat stands now
1. Virat is an emotional, guarded and a private person. He gives lot of importance to his family and relationships to the extent of personal suffering.
2. He is an independent man at the same time when it comes to his personal life. He can make important decisions on his marriage and when to throw his wife out and how to beg her back if needed. He acts according to his emotions. True he gets influenced by his family, but throwing his wife out and begging her back is his own doing. :)
3. He is the only person at the moment, who knows what Pakhi's intentions are, their past and present relationship status, his deal marriage conditions with Sai and the extent of his feelings towards Sai. And recently Sai's fondness and attraction towards him. Yes, he knows Sai is into this marriage but still angry about their last fight.
4. Only thing he is not able to gauge correctly is the extent of obsession Sai has for his deal word and her insecurities towards him. He thinks it is Sai's brashness that speaks rudely about him and Pakhi, but not her insecurities.
Now why he behaves the way he does...?
He being a thoughtful person and a responsible one, he 'overthinks' about the consequences. We should not forget that he loves Samrat a lot. Their bond is something which is not explored now a days but in the beginning it was shown that Virat has huge regard for him. If we keep that in mind, his actions towards Pakhi make more sense. HE IS NOT DEALING WITH EX-LOVER. HE IS DEALING WITH HIS BROTHER'S WIFE. For him, he has to live with these people for his entire life under one roof! Day in and day out he has to face her. It is not a small problem to brush off to start with.
He can easily expose Pakhi in front of the family. Sai is capable of doing it, Virat is not! For Sai, a wrong is wrong no matter who does it. She came from a nuclear family. And in her impulsiveness and her insecurity over losing her husband, she will confront her. (which I think will happen soon no wonder!). But Virat will not. He knows that he will not be exposing ex-lover pakhi. He will be exposing the intentions of his brother's wife, his bhabhi, elder DIL of Chawan family, and a woman...He thinks about all these things. Again, he is the same person who was very brash to her when she came to his room and confessed her feelings for him. He told her she is the third person, he warned her not to compare herself with his wife, he asked her to mind her own business and he cleared with her that whatever feelings he had for her were fleeting!! This is a big NO from his side. Like I said, he is an independent man when it comes to his personal life. He told her on face what she means to him. But he will not say all this in front of the family...
Now, coming to his muteness in front of Sai. I can only say from my observation of Virat's expressions and from above points. Virat doesnt want to bring Pakhi in his equation with Sai. He wants to rebuild everything with Sai afresh. If I remember correctly, not even once in their conversations or fights, he confessed in front of Sai that Pakhi is the person who he was committed to. Did he? (Except for one ocassion where he slipped 'pyaar' instead of 'dost' which added to Sai's obsession with deal.) It was Sai who guessed it, it was her who nurtured and nourished their ex-bond in her mind. For Virat, he brushes it off because he wants Sai to think that there is no trace of any feelings for Pakhi. He wants their relationship to be free from Pakhi. He expects her to understand this through his actions. If he has to come clean with Pakhi in words then he has to tell Sai that he once intended to marry Pakhi and she was the commitment that he was talking about during marriage. For all the reason we already discussed before he doesnt want to accept that in front of Sai. He brushed aside the Pakhi phase as a fleeting moment and he wants Sai also to not ponder on it. May be he is aware that Sai is prone to speaking her mind, and this information can give her more details which she would reveal in front of others casually. The previous statement is just a guess. The summary is he doesn't want Sai to give any importance to whatever relationship he had in the past. So he plays it casual in front of her and pretends it never existed.
Then why doesnt he confess his love?. I already expressed multiple times, that he wants to see where Sai stands with him. But if you observe his recent behavior, he knows Sai likes him, she is attracted to him. May be he was planning to confess with the kiss yesterday. But Pakhi's interruption brought him to reality that Sai is still planning to leave him. He has to first make sure she stays willingly and then he will take no time in confessing. He already made up his mind. To his muteness when Pakhi taunts Sai, I would say is his sympathy towards her. On the side, he is making umpteen amends with Sai in his own way by showering his love. Sai also sees that but doesnt want to believe it due to his initial deal words. She just needs a clear confession from his mouth.
And lastly his behavior towards Pakhi now is not insensitive...he knows her intentions towards him, so he is maintaining the distance. Pakhi's behavior has become redundant with Sai, so he laughed it off when Sai imitated her. He still is the same sensitive person who takes care of her needs as a member of the family. Yesterday near the dining table he behaved as a normal BIL should. He showed to Pakhi that he doesn't share any extra comfort with her but it is his duty to drop his elder SIL if she needs help. He still would not demean her in any way, especially in front of the family.
In summary, Virat and Sai are completely different people who handle situations differently. They are good at heart but respond to situations differently. Virat is grown up in joint family trained to hide uncomfortable things and play safe. Sai is grown up in a nuclear family with simple set of rules. She does not think in a way that Virat weighs everything before acting. He is the person who always knew Sai is good as a person but rebellious. Even in the initial phases of their marriage, he disapproved her actions not her intent. Her actions do not confirm with someone living in a joint family. And as a husband, only he could tell her that, no one else could. Sai might mellow down in future, not because she listens to her husband or not because she is weak or not because she is a woman, because she herself will learn how to stay in a joint family. (just my guess going by KD storyline)
PS: If Virat is so thoughtful why did he throw Sai out? He was dealing with Sai's 'betrayal' for the first time, that too from the woman he loves. So his emotions ran haywire.
Thanks for tagging me Lakhmi. I would not have written this if not for your tag. I was reluctant :)