Fridolina,
You asked me these same questions in a PM, but I thought I'd answer them here since they're all good questions and others may benefit from the answers as well.
First of all, I sometimes pull upwards very slightly with the right third fingers (using the second finger as a pivot point) when doing certain covering actions of the classic pass. For instance, if I'm doing a riffle pass action at the rear of the deck with my right thumb, or a dribble-pass action with the fingers at the front combined with the thumb at the rear, then I'll go ahead and use the slight pulling action from the right third finger.
Of course, I do this only because it blends away in the larger action of either riffling or dribbling the cards. I don't recommend the lifting action if the pass is being done without these covering actions. Although I don't typically do it, I think the lifting action could be camouflaged with jiggle-type covers as well. Be your own most critical eye as you progress with the move and you'll know if the lifting action is being properly blended into a larger action of if it's drawing unnecessary attention to the hands.
The other questions you asked regarding the degree to which the left 4th finger is inserted between he packets and how far the fingers extend on top of the upper packet were already answered by "saborfang17". Mr. Fang correctly replied "Depends on the person." While I could tell you what I do now, that information may or may not be of any value to you at your level of development on the classic pass (and its variants).
I've been doing the move for 20+ years and I have rather large and strong hands. In fact, I actively work on my hand strength on a weekly basis. What works for me may not work for you. Your best bet is experimentation and adjustment.
Which brings me to my last point. Quite frequently, I see someone post on the main message board (or other boards), or in a PM to me that they have some questions they want to "clear up" before they begin practicing a given move. The move in question is usually a difficult one, like a pass, or a false deal, or a false shuffle of some type. Invariably the person asking the questions says something to the effect of "I don't want to start practicing until I have most (or all) of the details so that I don't practice wrong."
Although this approach seems correct, I think it's a huge mistake. Maybe one of the biggest of them all. The thinking appears to be that you'll save yourself some time if you don't have to "unlearn" any bad habits that you develop by beginning right now versus when you have "all the details" about a move. This line of reasoning looks great on paper, but is almost always misguided. The biggest problem is that you can spend much more time "researching" a move to find those elusive super-details then you'll ever spend fixing a bad habit in the first place.
I've been practicing the classic pass and variations for 20 years now. I'm still learning things about the move on a semi-regular basis. And yes, I've had to unlearn and repair parts of the classic pass over the years that I didn't have right the first time. Those fixes were largely pain-free, because I had such an extensive base of mostly correct technique from which to build upon. If I had waited until I had “all the details”, I’d still be waiting.
I suppose that if you learned a classic pass in a completely incorrect fashion and worked on it for months and months, then I guess it's possible that those hours could be considered "wasted" to a large degree. But the chances of that happening are extremely remote.
It's much more likely that you'd have the basic action of the pass correct and might only have to tweak some small aspect of the move as you progress in the months and years to come. The vast majority of your time would be well spent. But if you're delaying getting started on the basic action of the classic pass because you aren't sure how far to insert your pinky, then you've wasted that time completely! On any one move it may not be that big a deal, but are you also waiting for the "perfect" bottom deal to come along before you start trying to learn one? Still not completely sure how big a brief to use on your second deal (to the point where you don't practice it at all)? This is a restrictive and counter-productive philosophy. Get away from it at once and start practicing.
Just get the hours under your belt with the basic move first. Most of the questions that spring to your mind early in your exploration of a move will answer themselves after a few hundred hours of working through the motions.
I used to joke with people that good instruction often didn't provide any meaningful shortcuts to people when it came to learning really difficult techniques. In other words, with or without great teaching, you still have no choice but to put in the hours when it's all said and done. I would tell them, "If you don't watch my DVD, it will take you about 15 years to master the second deal, the bottom deal, the center deal, the Greek deal, the MacMillan switch, the Diagonal Palm Shift, the Push-through shuffle, and palming. But if you do watch my DVD, then it'll take you 15 years and 3 hours."
It's only a joke, but there’s some truth in there too. There are no shortcuts when it comes to the tough stuff. Don’t waste your time looking for them. You’ll only fall father behind.
