Why is he acting like that? Pardon my being flip, but the first response I think of is: Who cares? That's something he can explore with a therapist or something I guess. Not your problem.
Originally Posted by
choublak 
I asked him why is he burdening me with all this stuff and he said it's because he has no one else to turn to.
I'm sorry your dad's still up to his "put-Choublak-in-the-middle" shenanigans. I remember when he first started with this.
Perhaps instead of asking him why he keeps putting you in the middle, you could reiterate your boundary that you're going to end the conversation if he keeps bringing this up. You may have to actually follow up: "Sorry Dad, I've asked you to stop putting me in the middle and I've told you that I would end the conversation if you keep bringing up your conflicts with Mom. Now I guess I have to follow through on that. Have a good night Dad and I'll talk to you later." Click.