It works now! Ok so.... I'm making notes while watching it. Let me first say that I think you're doing a great job. I say that because you asked for suggestions so I don't want this to sound like I'm criticizing you. But here are my thoughts on what might help....
First, I would adjust how you're treating him, especially since he has space issues. A good rule of thumb is to treat wherever you want his head to be. Flash never comes to me to be treated - he freezes wherever he is and waits for me to present the treat exactly where I want him to take it (which, for me, is with his head aligned and tucked/on the vertical since that's where I want him to hold it always). It requires a little extra walking on my part sometimes, but unless we're riding, he's not allowed to come to me for a treat. Rather, he should freeze (established during the "stand" game). Even when we're riding, he doesn't reach for the treat until I tap his shoulder on the side for the treat, but I think he's just learned that he might as well wait while I get the treat out and decide where he's going to get it haha.
Which brings me to the second thing - you're always behind him (which is why his ears are back). I would position myself directly to the side of his head or even a little ahead of him. This establishes "your space" in a basic sense, and he's not allowed to come to you. You can easily control his body from here and ask him to back up if you need to (which I would recommend training him to do ASAP to get him to step out your pace with more polite means). Having his body angled toward you automatically puts you at a disadvantage for him to be in your space since his head will naturally extend from that body and into your bubble.
I would also wait longer to click and decide exactly where you want his head, then be consistent. I think he's just moving back and forth naturally sometimes (getting comfortable, and knowing that a click means having a treat, but not really connecting it with why you clicked). For instance, you might have noticed that, even without a click, he turns away and then immediately back to you for a treat at about 2 minutes. Maybe ask him to hold it longer? I think where you position yourself will also help with this.
Never forget that the one who moves their feet is the one that's being dominated and pushed around. As for what's "appropriate" with clicker training, I still behave the same way I do as with any other horse that might not be clicker trained. The clicker is simply a "yes" signal when the horse responds to you how you expect them to. For example, even now when we're backing up, if Flash doesn't back up or doesn't do it fast enough, I start walking toward him fairly aggressively. He knows now that if he lets me catch up to his shoulder, he's gonna get a good poke/smack on the chest. He knows what he's supposed to do and it's his own darn fault if he doesn't respond quick enough. Yet, I still click and treat once he does what I was asking for to say "Yes, now you get it!" So, in your case, when you ask him to get out of your space and he does, I'd even click and treat. Maybe you should even make a game out of that - "When I raise my hands and move toward your head/shoulder, you move that part of your body out of my space!" You could even work work in zones, focusing on the horse moving his head, rump, or whole body over based on where you put the pressure.
Flash and I have the opposite problem. We need to work on a clear "come here" or "follow me" signal at liberty because he usually just freezes thinking he's supposed to stand or often starts backing up lol. It's never a problem with the lead rope because it clearly communicates what I want, but he knows better than to just follow me everywhere because we've really done a good job on the stand game - I can walk around the entire arena and he won't budge!