It probably hits at a little more than 5lbs using a more accurate scale. I've had 3 days of food in it. There's room for 5 days but I might be tempted to use a little more substantial pack for 5 days- maybe the Golite Jam, which can deal with larger weights. I carry about 1kg of food a day.
The short answer is yes. There is apparently a way to get it set up whilst wearing it but I've never got it to work...