For runny icing, just add a little more powdered sugar. I would add a tablespoon at a time and mix each time until it is the thickness you want. For your cakes, usually, when you leave cake batter out, it will not rise as much. So the only thing I can think of is either the oven temp or the pans you used. If you used different brands of pans, that could be the problem. If not, then your oven temp could be off. Hope that helps a lttle!
