Solved!
I made two adjustments that fixed the expression:
1) When I pick-whipped the menu effect, I had to add .value to the end.
2) Apparently the index of the first menu item is 1, not 0. So I needed to put v==1, not v==0 to reference that first menu item.
I will paste the working code below in case it’s helpful to anyone.
Thanks for the help!
v = thisComp.layer("Control Layer").effect("Dropdown Menu Control")("Menu").value;
r = thisComp.layer("Layer 1").transform.rotation;
output = 0;
if (v == 1) {
if (r < 45) {
output = 100;
}
} else if (v == 2) {
output = 100;
}
output;
//This way of writing it works too:
if (v == 1 && r < 45) {
100;
} else if (v == 2) {
100;
} else {
0;
}