Although tuna is nutritious just keep in mind it can't be a complete substitute for cat food since they have other requirements such as taurine that among other things it will help the kitten to develop his/her eyes.
I would stay away from cow milk (could cause diarrhea), give some tuna, chicken, for vegetables pumpkin or sweet potato or some good quality kitten food - grain free.
There are some raw feeding options in which case I would avoid poultry because sometimes when uncooked it could be contaminated with salmonella.
Raw feeding requires the addition of some vitamins and taurine though.
A while ago I found this video on a recipe for raw food: