I think you have the though process right in your example, yes.
It is usually quite hard to really interpret results though. FGS does not only affect the BU pushing range, but also the calling ranges as well as the "action behind".
In your example, calculating with FGS also means SB vs BB will be less likely to end up all in if BU folds (65% Push & 14% Call with FGS, instead of ICM's 85% Push & 17% Call.) This additionally loosens up the BU pushing range. You should definitely double check if the FGS ranges for villains are still realistic for your games.
In this particular spot i think FGS-1 may be too loose on the button, as deeper FGS is tighter again. But this is a rather unstable spot and the FGS results change quite a bit depending on the depth. (See: "Horizon effect")

