Skier,
1. weight bias is minimal - makes sense. If bias is forward, rotation will be around some point towards the tips with the heels sliding and displaced. Looking at Chuck Martin and Carmichael vids (as they ski today) they do quite big rotations (skis coming at nearly 90 degrees to the direction of travel at times) to reduce speed but it looks centered. Certainly those quick double turns as per young JLB (and today's Martin does them too) would be very hard if the weight isn't centered.
2. Up unweighting - Also heard it referred to as retraction - retract legs to body. As distinct from unweighting by jumping/popping which has a delay while the body moves up before it begins pulling the legs up.
3. Some ski instructors (JB and others) say they ski with shin contact all the time. One described it to me as his reference point. They say they do this whether they are forward, centered or back in the turn - good use of tibialis anterior I guess. Also had CSIA ski instructors get us to play the $20 bill game in the moguls. [Pretend there's a $20 bill pinned between shin and boot tongue and every time we lose contact it blows away. How costly was the run?] However I've not heard any of the CSIA folk propose putting a lot of pressure on the front of the boot. (JB does say that for high performance carving turns.)
On dolphin turns...the way I look at it the main thing is maintaining balance throughout the run. Now the feet will be slowed down as they meet the bump so to prevent the body from toppling over the feet we need to resist and/or anticipate. The size of any required response depends on the size of the bump, etc. Skiing with an upright stance does two things: allows better resistance/absorption of the upcoming load and lifting the knees in front of the torso (where the size of the bump requires) does re-position the BoS slightly ahead.
This winter I watched and overheard an APSI facilitator instructing his group - an L3 course by the standard of the skiing - to use an upright stance for that 1st reason. (I think the facilitator was Paul Lorenz but not sure.) Although I normally wouldn't read too much into 30 seconds overheard on the hill it is the stance we see many of the younger instructors (McGlashan, Lorenz, and others) use in their resort mogul vids.
Watching this vid (using slomo) of Nelson Carmichael in powder bumps in slomo shows what I mean on the second point. In this vid he isn't sliding into the bumps, probably because the pow was helping control speed or was thick enough to make that less of an option. (Or he'd had 2 coffees for breakfast...)
Or this one of some-one less immortal from a Donna Weinbrecht camp. (vid below for before/after viewing)
Dolphin moves are another option for resisting/anticipating. (Or just spicing up the run for fun.) It all depends on what the skier is trying to achieve and what terrain they encounter.