when you go to catch him and he turns and runs away from you,. What do you do?
A 4 acre pasture is pretty big to do this in, but what I do is if the horse turns his back to me, I make that an uncomfortable thing. I make a lot of noise, scuffle the ground , swing the lead rope into the ground, or do what ever, will startle him. Usually, he'll run forward a step or two , then turn and face the commotion. He didn't like that, but he will usually turn around and face it after the first couple of fleeing steps.
When he turns, you stop all motion, you turn your body off to the side a few degrees, soften your whole attitude and speak softly to invite him in. If he stands there just looking , you try backing off a step, and maybe off kind of angled toward his rear, but NOT closer. You are trying to draw him.
If he looks at you, then decides to leave, you allow him to make that decision (don't make a big noise until he has actually turned away) and make that an uncomfortable choice. You hope he'll do the same thing.
IF he runs away, you follow (I know, you can't right now. So this is your plan for when you CAN), and if he gets far enough away that he tries to start grazing again, you interrupt that. I have thrown a rock or a stick to do this. I dont' hit him but I make it land near enough to him to make him put his head up. When he does, I stop approaching, hoping he'll turn and look at me.
So basically, you make the choice to move away from you uncomforatable (try to never allow him to graze or rest too much) and every time he looks toward you, you offer total calmness. Eventually, and hopefully, he'll choose YOU instead and come over. When he does, don't put anything on him at first. He chose to come, so he shoudl chose to stay. If he rechoooses to leave, you restart the whole process.