@Eliz - I really have been trying this, to the point that we both get frustrated and sweaty, but will continue...I just don't know whether it's technically "good form" to give up without success after, say 30 minutes - is that "giving in?"
@aforred - Technically, no. I have a circle mowed in a flat section of field. I have pondered the possibility of putting together a makeshift round pen, but my previous experience with him, when I was first riding him and struggling with how herdbound he was, is that he will panic and run into anything in his way - me, tree, fence, etc...so I'm worried about injury to him or me.
@jazzyrider - I struggle here because it is not technically my horse, also because neither me nor the owners have any real margin in our budget. I've bought the training supplies (longe line, bit for the other horse, etc) and other non-necessities, but am not sure about the plausibility of a chiro coming out. Under saddle, he is, well, interesting. I am not sure whether his anxiety is from herd-bound issues or something else, but he is good on basics. I have noticed bucking when I ask for a canter, but right now I can't recall whether that was with a right lead or a left lead. He seems to be an overly-anxious horse in general, which makes me worry about making his anxiety worse.
It stinks that he(we) is(are) struggling so much, because he is one of the sweetest horses, loves people and children and any attention he gets.