Ok you need to get the Kaytee. That's what your bird needs to be healthy and it won't be healthy if you keep this diet. The Kaytee pellets aren't the best of the market but if that is what you have access to then that's what your bird needs so go get some. Also get a better seed mix, then take out the sunflower seeds. Canary seed or millet is ok, it's still fatty but slightly better than sunflower seeds. Or you can try and get a premade branded mix like prestige parakeet mix.
Changing the diet is difficult, he probably won't eat the Kaytee at first so you need to convert the diet gradually. Be careful with this because its very easy for the bird to starve. There should be threads about pellet conversion on here. Or you can make a new post about it. It's important to give fresh fruits and vegetables though please check what is ok before feeding him, there are many things birds cannot eat. Also birds are lactose intolerant so absolutely no dairy, milk or yoghurt!
If he's scared of the stick, don't use the stick. You can try this training outside the cage as well. But you need to just stay still and wait. Put your hand in the cage slowly and remain still if he flaps and runs and panics then you will not be able to do this in the cage. Try then having him on his perch and slowly putting your hand with some food as near to him as he is comfortable. Then leave it there and wait. If in one hour nothing happens. Stop try and again the next day.
Once you get him taking food from your hands you will be able to reward him for good behaviour.
for now let him settle for a few days. Let him calm down. He can still come out on his perch but just let him sit and do as he wants. Sit near his cage and talk softly but don't put your hands near just be around. All people in your house should move slowly and quietly around the bird make him very calm. It's easier to train a bird when it's not terrified and stressed. 
