OK... 1st, stepdown fixes are after the FAF... they are between the FAF
and the MAP.

The only IFR altitude that your are allowed to go below on an IFR
flight plan is the MDA or DA, and then only after you have the three
requirements satisfied as specd in FAR 91.175.

There is no provision for going below a step-down fix under an IFR
flight plan... VMC or IMC.

Gene