having problems with my 2 year old fjord gelding...

Hello folks,
I have been working with and training a two year old Fjord gelding named Django. A local farm who is trying to help place Fjords on small farms gave him to me and have been helping me train him--he seems to have a strong temperament, but recently things have taken a bad turn. A couple months ago he was out grazing and got a hawthorne branch caught in his tail, and it sent him running all over the yard and farm, finally calming near the gate and i was able to get him in and find the branch. Since that experience, he has started running, progressively when haltered, then with a chain over his nose, and we thought we had him by feeding the chain through his mouth. That seemed to convince him he wasn't going to get away...until last friday.
My daughter was up on him bareback as i walked him up from pasture, he started to seem a bit freaky and i was about to pull her down when he dropped and lifted his head and the chain dropped out--up the hill he flew. My daughter fell right next to me, had her helmet on, she was fine...he ran up to the clover patch. Every time he has taken off, i have caught him with no problem, and walked him around a bunch doing ground work, to let him know that is not ok--Yesterday was the last straw...I went down to get him from pasture and he seemed freaked, like maybe he had zapped himself or he was lonely or had a bee up his ass ??? We started walking (chain in mouth) and he was very balky, trying to pull his head away--i took him in 4-5 tight tight circles to calm him but somehow he pulled his head away and even with me pulling tight on the rope, he got away. didn't care about the pain in his mouth, didn't care at all. What am i doing wrong????? i know their instinct is to run, and his instinct got reinforced with the hawthorne, but i can't seem to convince him otherwise. My trainer friend is away right now, so he just doesn't get to go out to pasture for now, but he is ostensibly for little kids to ride, to pull logs out of the woods, to pull a sleigh...how the hell am i going to convince him that THIS IS NOT OK????
Thanks for any replies...
Becka Gagne
Schoodic Hollow Farm