This game is so much easier with a controller! I use my wired Xbox 360 controller, and works great. The only time I touch the keyboard is when I'm renaming my character at the Quick Change places.
I use the default scheme and once you get used to Right Tjumbstick click for melee and B button for crouch, it's smooth sailing. It's not like Crysis where there are too many things to comfortably fit onto a controller.
As far as I know, there are 2 toggle options, Toggle Crouch and Toggle Aim.
Like others have said, you need to hold down the run button, you just gotta hit the button and then continue moving forward and you'll sprint until you stop