The best way to get out of the back seat is never to get there in the first place There are discussions on here about when it's appropriate to be back, and there are some valid points in those threads, but for general purposes I would advise most people that being somewhat forward most of the time is better than getting aft at the wrong time. You mentioned pulling the feet back just before transition. That is not a bad recovery move, but it should be just that, a recovery move. As you hit the apex of the turn, the forces are building up and will begin to push you back as the bend of the ski is released through the end of the turn. This is the point of the turn where pressure control is required to keep you in good fore/aft balance. This is when you must be flexing using your ankle and knees.
Have you ever done any one-footed skiing? Specifically, try skiing on easy terrain with just the outside ski. Medium-ish radius turns, keep the inside ski off the snow but try to let the tip of that ski brush the snow throughout the turn. This may be easy to do, and if it is, take this drill to an intermediate run with some moderate pitch. Here you may notice that the tip of the lifted ski wants to come off the snow at the bottoms of your turns. Now do it again on the intermediate terrain and focus on keeping the inside ski tip on the snow by flexing the other ankle more. It is a move that is progressive through the turn. It's not a "set-it and forget-it" move. The flexure of the ankle increases as the turn progresses. If the movement stops, you'll find yourself in the backseat. Some people refer to this as moving along the length of the ski.
You also asked for clarification on your pop extension. What you're doing is similar to the old up-unweighting movements of yesteryear. The extension you're looking for should be a lengthening of the legs after the flexing phase that we just discussed in which you're ankles and knees are opened as you roll on to the new edges and use this extension to move your center of mass both up, and also across the skis, but with a caveat. If you move just across the skis, (ie. straight down the fall line) you're skis are going to continue across the fall line away from your center of mass and you'll have to either pivot using rotary movements, causing a skid at the top of the turn, or fall over because your base of support (your feet) have moved way out from under your center of mass (your body). So instead of just moving across the ski, you have to direct your extension to move your center of mass over your skis and also in the direction of the new turn. Some people love to call this a frontagonal move. I hate that word because we already had a word that meant the same thing, which is diagonal. There are lots of diagrams and pretty little graphics floating around the board that show this movement. Maybe someone can link some of them or point us in the right direction.