The bad part is he thinks he won again.
You know, he probably doesn't. It is a misconception that you, the handler, have to "win" every time. In some things, yes, it is better if you can finish on a good note--but not necessarily in the way some people believe. If you're training at something specific--say you are trying to teach the horse to sidepass, and he's not getting it, you really do not need to keep trying until you get a sidepass. That is just way too frustrating. Give it up for that day, and just finish up with something else--for example, back him up a few steps. He does that, you praise him and put him away. You've ended on a good note. The sidepassing can wait for another day. You have "won".
Now--in regards to trying on a bridle--at the last he put his head in the corner so you couldn't put the bridle on; if the bridle was still too small anyway then it wasn't going on him regardless--and no one can blame him for trying to have a too-small bridle forced onto his head. This really should have no effect at all on your next attempt to work with him. Honestly, I have brought a horse out to put some piece of tack on, only to have difficulty with it (think trying to put a killer blanket over a horse's head!) --maybe in terms of the blanket I didn't have time to mess with it at that point, so I put the horse away; next time I bring the horse out he really did not associate the last time with getting out of having the blanket on. I would expect to take the horse out, spend a bit of time getting him used to the blanket and then would get it on him (been there done that)--life was no more difficult because he didn't get it put on the first time. If I tried a too-small bridle on and he resisted having it put back on after adjustment & I determined it was still too small--I wouldn't even THINK of him seeing it as a win for him--I would expect it to have no effect at all on "next time". I think that you are psyching yourself out with this horse.
It does sound like Seven is getting the best of you in terms of leading him in the yard. It's not unusual for the horse you're working with to act up if his buddy across the fence starts ripping around. However, the horse you're leading should learn to behave when you are working with him--this behavior needs to be dealt with very firmly right from the start. If he acts up and intimidates you, so you put him back in the paddock every time he does it, yes, he has definitely "won" in that case. Do you have anyone who can help you with him? Someone who can give you some pointers on what to do when he starts rearing and pulling back? (By the way--is he gelded??)
When you walk him in his paddock and he tries to lag behind, I suggest carrying a whip so you can tap him on his back end and make him walk up beside you. If he pulls back or moves sideways away from the whip, lead him along the fence, with him between you and the fence. That way when you reach back and tap him on his rear end, he cannot swing away from the whip. Even teach him to trot in hand this way (if you don't already work him at the trot)--teaching him to walk and trot beside you, and then to WHOA from walk and trot will give you better control overall, especially when you make him do it your way, not allow him to lag along as he pleases.
Before you take him out in the yard to lead him make sure that he is well exercised. Longe him (if you don't longe him, that is a good thing to teach him--it's a good way to exercise plus a horse can learn a lot on the longe line) or just let him loose and make him move around the paddock. If you do have him out in the yard & he gets acting up too much so that you feel you have to put him back in the paddock, don't just turn him out and leave him--turn him out & then make him work. Make him do some trotting and cantering. When he settles down, take him out and lead him around the yard again. He will be worked down some so might be less inclined to play up. It would be good though if you could get someone to come and give you some pointers on how to handle it when he plays up.
I've never had to resort to using a chain on a Mini, not even on my bigger Bs. I don't even use chains on the taller Shetlands. I've had a couple that were very pushy and difficult to lead out, but I kept working with them--taught them to WHOA. Sometimes I carried a whip & positioned it in front to sort of remind the horse that he was to pay attention and not push ahead. In one case with a young stallion I just put my left hand in front of his face as I said whoa, it was a visual block that got his attention and he would quit trying to push ahead--he'd then listen and stop. After a few lessons I didn't need "the hand" any more and he was leading nicely. Rearing--and it hasn't been a big thing with any of mine--I give the horse a good shank and when his feet come down I back him up a couple of steps and then continue on as we were. I find no value in running the horse backward (as some people do) but a couple steps back makes the horse focus on me and he generally pays attention after that.
Grazing....I do let horses graze while I have them on halter, but I tell them they can put theirs heads down to eat, I don't just allow them to do it. If they try to graze when I'm working them I'll give them a snap on the shank (don't just pull, the horse braces on it and grazes anyway) or even tap them up with a whip if I'm carrying one (and I often don't have a whip) and say NO. I don't expect them to work hungry, but if they aren't out on pasture they often think they are STARVING for green grass, even if they are stuffed with hay. So, I work them and then let them graze for a few minutes. They learn.
