I'm going to treat this as a lack of confidence issue, rather than a lack of respect. Arabs (in particular) who aren't handled consistently from a young age trust their own instincts much more than they trust the people handling them. Out on the trail, this guy may be thinking, "This is scary, I'm outta here!" and not, "I'll get to go home sooner if I throw a fit with this wussy."

Here's how I've conditioned my young Arabs to the trail: take them out with other horses. Another horse can reassure your guy that this trail stuff is OK, and actually quite fun.

You say you can't pony your guy from your other horse- that's too bad, because ponying is an ideal starting point. Get someone else on a steady mount to ride out with, or, ideally, more than one. Put your guy in back, in the middle, in front for short periods that become longer as he gains confidence. LOTS of trotting, which gives horses something to think about other than the bogeyman behind every rock and bush. Lots of this, lots of this, lots of this.

When you do go out solo, lots of trotting. If you feel him starting to get nervous, put him into a trot. Sing while you ride- it will relax both you and the horse.

And I'd put him in a sidepull or something else bitless that would give me good control over his head. Make sure you accustom him to any new equipment thoroughly before taking him hacking with it.

If this isn't possible, for me this would not be my trail horse. If I didn't want an arena horse, I'd sell him. Life is indeed too short to ride a dangerous horse.