I also fixed thee aspect ratio to be exactly like Dooms. I only got it by plugging random values into PerspectiveFovLH and adjusting the viewport to leave out the area with the status bar.
The sky is up next. I'm trying to stay as close to oldschool Doom as possible, but I really hate the way the sky "bends" in it. Still not sure how I'll implement it, but I don't want it to look like the cylinder OpenGL ports use.