I've been hitting my head on the wall for a while with this, and I'm almost sure I'm overcomplicating it.
I have a variable for yaw in degrees (and also pitch and roll, but those should be irrelevant). I want to turn that variable into normalized 2D movement, so the distance traveled per frame should always be a constant.
I was easily able to to workout movement when I had a fixed view direction, but translating it with yaw is what's confusing me. I've been trying a combination of converting to radians, then using cos(x) and sin(x) but it only works if I'm looking in a certain direction.