I totally disagree with 'buying' a horse's friendship and trust with treats. It evidently is not necessary since I do not engage in giving treats or buying affection. A horse is a herd animal and develops a 'pecking order' out of each one's respect level for each other one. Pack animals, like dogs, will respond to treats. Horses just learn to get pushy and obnoxious.
The horse you describe as standing back and not barging in and eating when you are standing at his feed tub sounds like the 'perfect gentleman' with good manners. You want him to invade your space and the rest of use work hard at teaching them to stay out of our space. Had you ever looked at it that way?
What you describe as trying to sneak a halter on him and trying to get close enough with treats to catch him is completely counter-productive.
What I would do is put this horse in a round pen or an enclosure of some kind. A square corral works just as good as long as it is not too big to keep walking around and keeping a horse moving when you want him to. Then, just make him move around in it for a while. Any time he buries his head in a corner (if you are using a pen with corners), pop him on the butt with a rope. Wave and slap the rope around until the horse starts to look bored with it. I make a horse change directions many times. I carefully watch what direction they reverse directions -- either toward me or toward the fence. If they reverse toward the fence, I yell at them and haze them harder with the rope. If they turn toward me (not real likely at first), I back up and stop hazing them. Most horse keep going and the handler looks for the 'licking and chewing', lowered head, lessened 'flight' response, etc. When that happens, stop and as soon as the horse looks at you, drop your head and back up. You try to 'draw' the horse to you.
I do not have time to go through all of the details, but they have been posted many times. Look up 'join up' and 'round penning'. There are many detailed explanations of just how to do it and just how it works.
In about 10 to 15 minutes, you can have even wild horses hunting you up and wanting to get caught and haltered. It works on all of them and it works 1000 X better than trying to bribe and buy one's attention.
I never 'hide' a halter and get all new horses I get in to hunt me and a halter. Most of them drop their heads and hunt the nose-band on the halter after just a few times of being caught.
Just remember, trust comes totally from respect, not from bribing a horse into wanting to be near you. Like everything else, the method that works best is to make the right thing easy and make the wrong thing (walking off) a whole lot more difficult.