OK, I watched all 3 videos. For what its worth here's my take on what is going on. And what you might do about it too.
I don't see an aggressive bull, yet, he is just playing at this point. Not much different than a well fed feedlot animal, or any other young animal that is fed fairly well and feeling it's oats. The only problem I see with that, is that he sees you as a herd/playmate. Now, if you don't do something to change how he views you soon, you will have a big problem. We had an aggressive bull a number of years back, he was only a problem for me, DH didn't have any problems with him. He was bad from the day we unloaded him as a yearling. I couldn't even enter the pen with him, I'd walk up to it to feed him and he would be pawing the ground and blowing snot. I spent one winter throwing feed OVER the fence, he bred cows for us 1 season and then he went to town. I don't see any of the real aggressive signs in these videos.
As a few others have suggested, you need to carry a stick, and be prepared to use it. A good stiff swat to his nose when he comes running at you should be about all it takes. I noticed in the 3rd video that you had a fork and used it to block him when he came running up. That's fine, but a good smack to his nose with the fork when he came running would have done a lot more to gain his respect. It might take you a few times before he really gets the idea that you are not a playmate. You need to do this NOW, he's only going to get older and bossier. Quit scratching him. Treat him like a bull and not a puppy dog. To top it off scratching him on the head is just adding to the whole situation. It has been mentioned before, scratching him on the head just encourages him to be pushy.
Also, cut the barley out of his ration. I don't really see why you would be feeding it to him, he's in really good condition as it is, and good quality hay or grass should really be all he needs. The barley is part of your problem, the extra energy has to go somewhere and it adds to his playfulness. He also likes the stuff and associates you with it. So when he sees you he gets excited and shows it.
I would also give him a companion, whether it is a cow or a steer, whatever. I know you said you did, and it didn't help, but cattle are herd animals and he will be happier with a friend.
And one other suggestion is to give him room. I can't tell how big his pen is, and it certainly might be big enough, but just having enough room to move around in might help too.