Re: "Five Lessons: The Modern Fundamentals of Golf" by Ben HoganI think every Hogan devotee over that past 60 years had faced the same dilemma. I am not a pro, but I have carefully read Five Lessons a bunch of times, so I'll just share what I see from the book to answer some of your questions.
1. You have to put your body in what ever position it needs to get too so you can have the imaginary plane of glass resting on your shoulders. The glass angle is going to vary on your club selection. So for a driver it will feel more upright. For a chip with a lob wedge, you will feel more bent over.
2-3. I could never figure out the life line thing. I would do exactly what Hogan shows. Palm facing target, fingers extended, put the club below the palm, as he shows in the diagram. Hold with the two middle fingers. The folding the palm of the right hand over, because there is a lot to fold over, has always been confusing. So I bought a Mark OMeara golf grip, which is supposedly based upon Hogans grip. Then I turn the book upside down and try to figure out if my grip looks like Hogan's grip as he sees it.
4. Remember, in the overlap grip he is specific. It locks inbetween the middle and index finger. Also notice that he darkens the right pinky, meaning he is emphasizing that part of the grip.
5. The answer to this question is what is referred to as the Mystique of the Hogan swing. People, since the books publication have benn trying to figure this one out. The person who can figure out your question number 5, will become an instant millionaire and the most sought after golf instructor in the world.