Like you, I'm an old-school racer. Learning the new-school slalom technique was like learning to drive all over again, in some respects.
I agree with Rusty's assessment: most of your pressure emphasis in the turns is after your skis have gone through the fall line - very old-school. I also see a lot of rotation of the skis to set them up for the edge set, which is an old-school maneuver that could also be indicative of the rather non-SL boards you are on.
I, too, resisted the move to specialized skis for short turns for a long, long time. I just couldn't be convinced that a shorter ski would work properly for me, etc.
But then I demoed a slew of shorter skis. The first pair of "shorties" I bought were a pair of Atomic SX:11s in a 180cm length. I loved 'em when I demoed 'em, and eventually bought a pair. They are heaven in GS turns at high speeds. And my technique adapted quickly to GS, as the new-school motions are a bit easier to adopt in the longer turn structure.
It took me a little longer to buy into the short SL thing, mainly because I'm tall and was wary of my balance on shorter sticks. I demoed a bunch of SL and short-turn carving skis in 160cm and 165cm lengths, but felt weird on them for a while.
Then I decided to deconstruct my technique and rebuild it for new-school SL turns. It took me weeks of simple motion adjustment, then rebuilding the turns to match. I watched a lot of World Cup SL skiing from the past two seasons, both online and using the DVDs produced by the US Ski Team and Alpine Canada. I also did some work with my old racing coaches, who are up-to-speed on the new technique - a good thing, as they showed me some useful drills and dryland exercises to try (living in a city, it's tough to hit the slopes as often as I'd like).
It was a lot of work and frustration, for sure. But it came around, and then I tried the Atomic SL:12, the Fischer RC4 SL, the Dynastar Contact 11 and the Blizzard Sigma SL when I was in Austria.
And things clicked, and WOW - what a difference!
The new-school technique will feel a bit out-of-control at first, for sure; after all, you're fighting muscle memory and instinct, which is really, really tough to swallow if you were a confident racer. But give it some time, and have a sense of humour about it, and you'll do fine.
Tried the technique in some SL gates a few weeks back, and it was an amazing difference: I felt very much in control, with my skis working for me, rather than me muscling the skis into submission.
You'll get there, for sure. You have a great technical base on which to build, so it should come easily. Do get a pair of modern SL skis or short-turn carving skis - they're worth their weight in gold. Make sure they have adequate lift under the bindings, because once you start dialing in the angles, you'll need 'em!