Mamji had once said "Kya Sonakshi Jaisi Bhali Ladki Ka Dil Todkar Dev Ko Bura Nahin Lagta Hoga ?"
I think that is the main problem with Dev right now. He is guilty of hurting Sona and hence unable to be at peace with himself ... His insane behavior might continue until he has a straight heart to heart conversation with Sona.
I guess after Sona talks to him and takes promise from him that he will never see her again, never follow her ... etc ... He might feel better .. And then we might be able to see a sane Dev Dixit !!!!
Looks like even Sona might break her engagement with Rithwik after that episode .. !!!
And then both Sona and Dev might go their own ways for some time ... before they meet again ... !!!!