It sounds like the poor horse is just as confused as you are. He is very insecure. He has no idea that he is supposed to bring you "joy", he is only acting in the way that his environment has set him up to behave.
First of all, treats as bribes are not a good idea, if catching is the problem, the girl that brought him a treat is not going to make him happy to come willingly, it is only reinforcing the poor behavior. It is very normal for insecure horses to be inconsistant. They experiment with all types of fight and flight behaviors before they will either 1. Get a response from the behavior or 2. The need for the defensive behavior is gone. I don't mean to shelter him from things, but when he no longer feels the need to be defensive.
Remember, the most important thing to him is going to be his safety. He is good at being a horse, he is not good at following a human's training program. Put your goals aside for a while and instead get to what he needs, his confidence. Its not about giving him treats, its about being his leader and giving him boundaries and rewards that mean something to him as a herd member. A good scratch on the withers is a great reward. I personally have never witnessed one horse walking up to another horse in the pasture and giving him carrot, yet they stick to one another like glue for the safety and security that the herd offers. You need to offer that same security to him through yourself.
Start with what he has problems with, if you are having any issues with catching, then that is the first thing to solidify. Catching doesn't mean putting a halter on. You can get a halter on a horse without truly catching it, and you can successfully catch a horse without a halter. I'm referring to catching the mind. I would recommend getting a good trainer to help you. Horses don't follow a rule book and there is more to understanding this guy than what can be sent over a forum message.
Horses are a product of their surroundings. Its very easy to blame them for behavior that we don't understand. At his age, its pretty simple to conclude that he isn't solid enough in his basic skills to be able to carry them without assistance. I definitely wouldn't say this is just "how he is", this is only "what he has become" and it is very possible to change it to something better, but it can take time.
As far as the time period goes, it varies with the state that the horse is in. I've brought in some emotionally damaged horses that take months to finally settle, yet I've brought some horses in that are "with the program" in no time at all. The amount of time that it takes them simply shows the work that we have to do. A month of time is not long at all for an insecure horse, especially when his environment isn't giving him what he needs to be consistent.