
I believe that is too much of a transition. I think it is best to add a little at a time, not a whole meal, so that would certainly be my guess.
As for which food, they are all probably acceptable to various standards.
So it is up to you and how you want to feed him.
You could search the posts here about food and feeding and see lots of folk have differing ideas.
My dogs are fed a mix of raw, Arden Grange complete, (sometimes I change AG) and domestic leftovers.
Karen