"Good for icy conditions" and "doesn't catch an edge" are typically mutually exclusive characteristics. At 180 lbs and being a beginner, anywhere from 155 to 158 should be just fine. My first board was a relatively flat, traditional camber 156. I wouldn't consider going as short as 153 unless he is doing 90%+ of his riding in the terrain park.
I am 5'7" and my weight goes between 170-180 depending on how much running and cycling I have been doing. Unless he hits the gym HARD (and diets, and runs many miles each week), he won't be losing 10 lbs for a few months.