When I was an inexperienced horse owner, I had a 2 year old stud colt. That colt did not respect me at all, would come after me, and I had no idea how to assert myself. One day he bit me so badly in the chest that he ripped my shirt off and I had to go to the hospital. From how things are going, you are in for this or worse if you don't do something now. This situation has to do with both his age and his testosterone. It will definitely help to get him gelded, and you will probably see a difference within the first couple of days because of his age. Right now, if you are going to handle him, make sure you have a stud chain and a dressage whip, and possibly a dull nail or something that if he REALLY invades your space or tries to shoulder you, as young colts often do, he can "run into" the nail. When he refuses to walk forward, you crank that stud chain and tell him to back up and get him out of your space. Until he walks forward, you bring the pain and get him out of your space. IF he comes at you, you go for him with that dressage whip and crank him with that chain. When he comes at you, if you back up or try to get away, you are giving in. Just being able to stand your ground will make him respect you that much more. He will no he is not allowed to invade your space, and that will make him safe to handle. If you don't stop this now, he will probably start standing up on you and trying to get away, and let me tell you, that is not what you want!
Just know that there is so much to learn from this experience. I am very confidant at handling stallions now, and I can do it without artificial aids. Just do what you can and don't get discouraged! You CAN and WILL fix this situation.