I think having Nutrical on hand is a good idea for everyone's first aid kit
. It is sometimes needed for adult dogs too.
I would feed by what it says on the can. Nutro has had a lot of problems w/ their food, is he doing okay on it, btw?
At his age/weight - and bc he is injured, it may also be good to free-feed kibble so that he can manage his nutrition needs at all times.