I have to disagree. You don't have a few problems. You only have one problem, and once it's fixed the other issues will fall into place. As already said, he doesnt see you as his leader. He's not necessarily being 'bad', he just simply doesnt see the need to show you the respect that he would to the lead horse in a herd. You need to be the lead 'horse' in your herd of two.
Rule #1-he is not allowed into your space (think a hula hoop sized circle around you) unless you have invited him in. YOU can go into his space (think an oval shape around him) anytime you want to. No exceptions. Simply making this his (and your) new reality will make a huge psychological impact that to him screams that YOU are the leader.
How do you keep him out of your space ? First of all you must be aware, all the time, of his intent, yes, just the intent of leaking into your space. Each time, you either create a commotion-flapping your elbows might work--or, better yet, teach him a back up cue that allows you to stay in place, but gets him to back away. He who moves his feet is not the leader. He who stays put, but causes the other to move their feet is the leader in horseville.
You can learn this and much,much more by 1) studying a Natural Horsemanship's program-ie Pat Parelli, Clinton Anderson, Chris Cox, Dennis Reis,etc....., or 2) A good trainer in your area who either is a self proclaimed Natural Horseman, or leans in that direction.
Rule #2-Following Rule #1 does NOT translate into needing to be 'mean' or hitting the horse !! In fact, be as soft as possible.....but as firm as necessary to get the response of him moving out of your space. If you always start with the firmest request,a very human tendency.... you will soon dull him.
Hope this teeeeny bit of info is helpful to you! This is a very large topic with loads of great educational materials out there.