Yes, Ray has given you great advice. It really is too soon to try and train. It will not build trust any sooner, it will probably do the opposite. Just give him time to settle in, talk to him, encourage himi, praise him, give him treats.
I agree with having him vet checked. I WOULD not clip his wings, it can be very stressful if he is used to flying. He won't hurt himself, greys are very skilled fliers. I would have his nails and beak checked.
You will have to gradually change his diet, there is way too much sugar in fruits, you should try some cooked veggies, it can take time before he will try them, but eventually he will.
My amazon does not like my hands in her cage, since it is her place, I respect that and don't try. She will allow me to put her back, but I allow her to get out, it keeps her happy! You should be able to ask your bird to step up, and when he does, praise him. Don't go overboard. In time when he is settled in, he will want to please you.
Remember, this bird has NO idea, who you are, how kind and loving you can be, if this is a safe place or a scary one, nor does he even have a clue that this is HIS new home, his forever home, or if he will be hurt or abused, or loved and adored forever. He will learn these things over time with patience from you, but it will take time, slowly he will understand, but it has to be in his own time, not pushed on him.
Sounds like you only want the best for him, and he will learn that, and where does, it will be well worth it to you!