cockatiel EXTREMELY scared of everything!

hi there! my whiteface tiel, toby, is awfully terrified of everything! when i'm changing his food and water, he constantly flies around his cage, kind of like thrashing around but not extreme thrashing. while he does this, he lets out high pitched screeches and gets really scared. when people come a little too close to his cage, look at him for a while, or if there are outside sounds he doesn't like, he screeches and tends to pace around his cage, all terrified i feel terrible watching him get absolutely horrified, though he recovers shortly after, but only if you pay no attention to him. i just really need help on taming an extremely scared tiel! i don't want to stick my hand in his cage and make him get used to it, that seems a little too cruel to me, especially since he gets scared from people just standing close.
heck, i don't even need him to like come to me, i just want him to know that it's okay. i could use some advice! please do help! <3 i appreciate any response given <333
also, he isn't enticed by millet in the slightest ( surprise surprise )

this post seems like a downer- on the bright side, he's been adjusting well to diet transitioning from seeds to pellets and veggies! :") he chirps as he eats and it always warms my heart <3