Well, for starters, Dev better apologize to his wife,even if it is for the nth time!
Secondly, he is wise enough to understand the meaning of Sona's note and explain to her his intent, as someone nicely put it in another post, was to protect her from the Dixit storm. I know what Sona will then tell him - that two in a storm is better than one... and Dev must accept this fact..
Thirdly they must patch up by love... I have seen some crazy ideas of resort, hotel, car. Etc..etc.. but patch up they should..it is better they go home to the Bose house or Dixit house and for what normal friends and lovers do... no imaginations here...
Finally, Dev must take a resolve to include Sona in his life completely. She is now his only strength in the emotional storm that Ishwari and Neha and GKB can create...