On a 3 degree glideslope, at a normal CAT1 DH of 200' you will be a touch over 1km from the threshold. Obviously in 550m vis this is not sufficient to see the threshold, but (talking European here I might add at this point) FALS should be at least 720m so you will see the approach lights to continue.
To answer the question at what height will you see the threshold, well some very rough calculations would suggest to me approx 95'.