SSHF wrap up

I should be ecstatic that Duke and I finished 9th out of 29, but I'm not because we were tied for 3rd until show jumping, at which point we blew it.  Two rails.  And an UGLY round.  We blew it less badly than other shows ("only" two rails), but I stewed most of the way home because I don't know what I'm doing wrong in show jumping - at shows.  I don't have any idea what it is, so I don't know how to fix it.
I applied John's theory from last time (he's stiff in the neck) by bending him before we started warming up, had exactly the right length of warm up (and John's help), and then bending him again before we went in the ring.  But when we went in, he grabbed the bit and ran like fucking satan was chasing him.  So I made a mistake there, which was to grab back.  When he's nervous, I have to LET GO.  So, ok.  And then my other theory is he's just not distinguishing me letting him run on cross country from the next day, at show jumping.  And he's all "yippee" and takes off in the ring?  But that doesn't quite work because he doesn't do it in show jump.
For dressage, we applied John's half halt lesson, and also, I was relaxed because I thought there was no chance we'd place in a class of 30, so I was just enjoying the ride.  And Duke was great.  The scores were very fair, as were the comments.  It wasn't perfect, but it was a decent ride.
For cross country, Duke was a rock star.  It was chilly and drizzling, and the first 1/3 of my class sounded like a massacre.  He handled everything like a champ - all the jumps we jumped in the spring we jumped even better (and faster), and he did great with the three new fences too.  He was AMAZING with the "hard" fence - a log with a drop down to a road, and you had to look left in the air to make the turn, and he DID IT.  By the skin of his teeth, but we made the fucking turn in the air in one stride.
He was great in the trailer, in the stall, being braided, in the cold, all that stuff.  So I don't know why I'm focused on the two rails - I think it's because I can't figure it out.  Like if I was making the same mistake every time, ok, I'm a dope.  But I'm not - I change something and then something else goes wrong.
I walked prelim and it looked ok.  About four of the fences were huge, but I thought I understood the technical questions and they didn't look too hard.  But for god's sake- the show jumping ...