I feed raw (although not premade) and I feed them twice a day, feeding more than once keeps their blood sugar stable and helps to prevent hypoglycemia.
I'm not sure about your defrosting questions as I don't know how long your premade will take to defrost but i'm sure someone else will.
As long as you vary the type that you are using it does not matter wether you feed both types in one day or different types alternate days. As for how much to feed them, I simply observe their weight and condition and alter how much I feed them (more or less) using them as a guide. Much like you would for yourself or your family. If he looses weight then up it and if he puts weight on then lower it, if he stays just right then you are feeding him the right amount. Different dogs have different metabolism rates so two dogs that are the same weight could need totally different amounts of food.
Well done for being brave enough to give it a go. You never know, once you are confident feeding the premade then perhaps you will be brave enough to go ahead and start doing it yourself. Good luck
