The Dogan

[Letti]

When I first read about it it was really hard for me to understand what the hell was going on. Now that I am rereading it at the third time I think I can understand its system quite well.
But let me think how you understand the Dogan.
So it's a fantasy place inside Susannah's head. Here she can control her body easier.. it's like having a computer inside your head.
But could everyone have such a thing? Such an inside room? Could Roland have stopped or at least slowed down the infection he was suffering from if he could have stepped his Dogan in his head when he was dying on the shore?
Or is Susannah just this special?

And...

if it's just a fantasy place... how could Susannah see that the chap's eyes were blue? At that time she had no information about the chap's dad. Or did she feel it anyway?
This Dogan thing is not absolutely clear for me.
I have been thinking about the Dgan for long, please join my friends.