do yourself a favour and just buy a N64 controller and USB adaptor. And it really should be a real N64 controller. I've purchased like 5 fake ones both USB and standard N64 ones and they all suck donkey balls. I finally broke down and bought some real ones and the difference is amazing. You still gotta calibrate it correctly and it's difficult to move the joystick very small amounts, so I added a mod that when I press the space button the sensitivity goes down by 50%. This allows me to aim better or walk really slow. Then I press the space bar again and go back to normal.

WASD + mouse will not really work for N64. I mean, the way you have it now is pretty much as good as you can get it: you move your mouse forward and it's like moving the joystick forward. You move it back, and it's like moving it back. There's no way you could set it up so it only moves when you move your mouse - that's retarded. Imaging playing Zelda where you hold the joystick forward to run. If it only moved when you moved your mouse, you'd have to constantly move your mouse foward.

Anyway, maybe you could set up the dead zone to be like 50% or something. Then you don't have to move it far to get it back to the "middle". But seriously, just get a real Nintendo N64 controller and USB adapter.

Or just play Doom for PC.