Admittedly I haven't read Dostoyevsky's work (I plan to read Crime and Punishment. Have you read that? How is it?) so I have no way of knowing if you're trying to set the same mood or style as the author. One thing I'm interested in is what the mindset of the character is in the opening paragraph. In some lines he seems sophisticated and refined, at others he sounds like the guilt is driving him to the brink of insanity. Sentence structure can convey a lot about the mindset of a character more than what they're actually saying.

For instance, I can make him sound brooding and psychotic:
I’m not sorry I killed Old Nikolai. He was a pathetic excuse for a man. Did not deserve to live. Must remind myself that. It doesn’t matter that he was my father; he deserved to die. I am glad I killed him. But there is a price I have to pay for purging the world. I’m currently shut off. Some nasty, dark place. Waiting for the end of a rope or the shot of a gun.

The light is fading. Can’t write in the dark. I shall retire. Have to remember I’m better off than Old Nikolai is.