Excellent, youthful, enthousiastic skiing! There's no fear in those eyes, and that'll pay off big. And good on ya for having the cajones to stand in front of the firing squad (even if we are just firing bean bags).
Here's what I see, and it's been mentioned before. Absorbtion. Absorb, absorb, absorb! in those videos, there is basically none of it. And what ends up happening is that your stance is balanced equal to if you are standing on the front side of a bump, which is way too far back once your skis contact the snow in the trough. The whole thing you hear about speed control happening through absorbtion is true - to a point. What absorbtion does, is allow you to control your speed. In your vids, you notice you are basically flying from bump face to bump face, slamming into the front of each one. If you absorb, you'll have ski and edge contact with the snow all the time. This is what you need. That edge contact will allow you to turn your skis to get your body (center of mass - CM) to move across the fall line just a bit. That movement of the CM across the fall line will keep your speed in check and allow you much more control. Or you can just pivot and skid the skis a bit for some speed control if yo need to. Your stance needs to be in balance with the pitch of the hill, not the face of the bump. That way, as you roll over the top of the bump and are in contact with the snow on the back of the bump, you'll still have control and not end up doing a butt plant.
To be honest, I saw a lot of people comment about your poles. I'd completely ignore the poles for a while. What is being seen in the poles is just a symptom of the balance and absorbtion issues.
Rather than just telling you what issues I see, I figured I'd also help you out with some ways to work on those "opportunities for improvement"
. Here are a couple of things to try on the hill. First, just slow it way down, but keep the exact same line. Yes, pivot the skis under you a bit for speed control (
: ). Just ski it slow and don;t let the skis ever lose contact with the snow. Especially the tips. Now, here's the tricky part.... Don't let your hips/chest move up and down as your skis move up and down over the bumps and through the troughs. You'll feel like your knees will be in your chest as you come over the tops of the bumps, and your legs will be fully extended when you are in the troughs. It's fairly hard to do when you are going really slow, because it requires so much conscious (and seemingly exaggerated) movement. Because you are going slow, the skis won't be flying off the tops of the bumps, so the movement may seem unnecessary, but it's just an exercise to learn the movement patterns for when you speed up. It may help to unbuckle the top buckles on your boots and loosen the power straps so that you get more range of motion from your ankles.
Here's another trick. this one will help you learn those absorbtion (active retraction) and extention movements. You'll need slightly more speed, but it's still done somewhat slowly, and may require taking your skis off and doing some walking/hiking to set up. Go into the woods and gather up 5-10 somewhat straight, skinny sticks about 2 feet long. Place them on the tops of the bumps that make up the line you are skiing. However, place them about 6-9 inches in front
of the top of each bump (just as it starts to round over the top). If you skied the run the way you normally would, you'd be slamming into those sticks, with the skis hitting the sticks a few inches in front of your toe bindings. Now here's the hard part. Ski the run without letting the skis touch the sticks. Basically, go straight over them, but hop over the sticks so that the skis don't touch them. This forces you to actively retract as you are going up the front of the bumps, and not to extend off the tops of the bumps as you had been doing. After you jump the sticks with the tips, in order to keep the tails from landing on the sticks, it forces you to get forward and lift the tails and drive the tips down the back sides of the bumps. If you can do this, then do the same thing without the sticks there, then you're golden.
Also, in your original post, you mentioned something about folding at the waist. That's not an issue. It's not happening at all, so don't worry about it. What I would say though, is that if you feel like you are folding, you need to start learning some new feeling of bending at the joints. All the joints - the ankles, knees, hips, spine. You're probably used to skiing very tall and stiff, and have gotten used to those feelings and think they are correct, when really, you want to learn to feel what it's like to bend the joints and ski that way all the time. Skiing tall is relaxing because it's less fatiguing, since you are standing on your skeleton, but standing too tall all the time has some significant drawbacks. Not that you want to ski too compressed or bent over, but it'll feel that way until your body gets used to how much is enough.