ive had him for almost a month now, im being extremely patient with him, not pushing him into doing anything, im avoiding proglonged eye contact, im keeping my voice soft, when i got him home i left him alone for 2-3 days, then slowly started introducing myself, i put my hands around the cage and into the cage like youre supposed to, i went about my day in the room hes in, and i spend most of my time here as well, he's heard my voice quite a lot and has seen me frequently. he grinds his beak, sings and moves around and plays with his toys sometimes, but hes still cautious of me
ive even gotten him to eat from and sit on my hand, but he still lunges and hisses at me sometimes, and now he wont even get out of his cage? no trauma or bad experience has happened to him in my house though when i tried hand training him he wasnt happy that my hands were coming towards him (this was recent) also he did come from a petstore and had been there for at least a year, am i doing something wrong, is this normal? any suggestions as to what i should try?

also a few notes that might help?
- when i let him out i dont force him out but i do have to carry/bring down his cage from a dresser and thats always something he seems to hate, but i dont have any room for him elsewhere :^( when i do bring him down i put his cage on the floor, and the first 2/3 times he came out of his cage he came out flying (trying to, hes clipped) and screaming, they werent necessarily bad experiences i think, but i feel like he doesnt enjoy coming out, i have two perches for him to sit at and the only things he's done is walk around my room, sit on the perches, and he's had to try hand training step ups

today i started hand feeding him so his bowl is now out of his cage

tldr ive had my cockatiel for almsot a month, done everything i can to make him comfortable, and he seems like he is but he's still biting and scared, how can i fix this?