Work outs near the barn......
Well let's start where the horse is at, in the round pen. If are not using a lunge line, then start using one to get him accustomed to it. Make sure he is turning on command after a lap or two, turn him around and do it again and again and again. They cut the circle in half, lunge him back and forth on one side of the circle so that he is moving back and forth in that half circle, then do the same on the other side, that way you are assured he will move, stop and turn using both sides of his brain.
When he is accustomed to that, and just as impostantly you are accustomed to it. Move outside of the round pen and do the same procedure. When you are both proficient outside the round pen, then take him near his stable/barn and work him back and forth between you and the barn doing quarter to half circle lunges, always making him pass between you and the barn, slowly and I mean slowy reduce the distance between you and the barn, the part will naturally lead to his next lesson, but for now work him back and forth by the barn, never let him rest between you and the barn, but only when you lead him out away from the barn area. Or at least with him on the outside of the circle and you between him and the barn. I have seen the pictures of your horses and they are beautiful horses. However this one is a little barn sour and disrepectful. Remember, lungeing for respect is NOT running your horse around in circle to make him tired, it is gaining control and respect of the horse, by making him move his feet and making him stop his feet, then making him turn and move his feet again. If you can make a horse move his feet in a herd situation, you will be the dominate personality in the herd.
So instead of lungeing him for 2 hours, lunge him for 45 minutes, always end on a good note and when you decide he has done well enough to end.
With the remaining hour start working on his lateral flextion, stand first on his left side between his withers and hindquarters, pull on the lead line, pulling his head towards you, as soon as his head turns towards you immediately slacken the lead line to give him the release he will be looking for, then do it again and again until you can stand at his hindquarters and with very little pressure bend his head towards you so his nose would touch the stirrups on you saddle if it were on him. Now remember everything you do on one side of the horse you must do on the otherside, Now be patient, if you only get his head back about half way to what would be the stirrup position, that is ok for the initial lesson, but do that on both sides, you will find greater resistance on one side. Usually the side you have spent less time on.
Also note this, if you have not been working on the horses lateral flextion, then when you pull back on the lead line he will probably turn his whole body around to find the release from the pressure, keeping the hand nearest his body on his body, move with him until he stops moving, keeping the tension on the lead line, when he stops and turns his head back to you (which means he had found the right answer) then quickly release the tension on the line, showing him if he want the release, he must turn his head to get it. Do not worry about vertical flextion, lateral flextion is truly the key component to getting vertical flextion.
Another thing you must do is to convince him you can get him to move his feet, take the lead line and walk towards his hindquarters, swinging it around in a vertical circle nearest his hind end. If he does not disengage the hindquarters and move them away from you, then spank him on the hindquarters as you walk to them, he will move them. Now spanking is hindquarters with a soft cotton rope is not beating the horse, it is used to get his attention and soon enough when you raise the lead liine towards his hind quarters he will automatically dis engage them and turn them away from you. When a horse shows you his hindquarters when you approach them, not always but usually it is a sign of disrepect. You will want to teach the horse repect by making him move, stop and turn his feet. If you can control the feet if a horse you can control the horse. This is herd behavior... Watch a herd sometime, see the dominate horse back up to another horse pinning it's ears back and suggesting, if you do not move, I am going to kick you, if the horse moves he is submiting to the dominate horse and accepting his lower ank among the herd. If he does not move he will be kicked until he moves or fights back. So if one horse can control the feet of another horse then that horse who is in control is the domiate horse and is to be respected. You will become the dominate horse by controlling your horses feet.
Use only the necessary amount of pressure needed to accomplish each task, to much pressure will help confuse the horse hindering it's ability to find the right answer. When it finds the right answer release the pressure immediately.
Needless to say be loving him by rubbing you hands all over his body at each rest time and at each time you release the pressure.
One more thing, so I know you understand about appropriate pressure. When I train a horse to back up, I first say BACK and repeating it over and over again, if he does not back up, I add wiggling the lead line as I say back, this adds more pressure, if he does not back up still, I add swinging my training pole back and forth as well as wiggling the lead line and saying back, and so on and so on, it does not take long for the horse to start going back on the minimal pressure of saying BACK. One more thing, one of the ultimate things a horse can do showing repect is to back up when you tell him too. So add this exercise to your list of training regime.