Jim, I can give you a definite answer on #4. I have a 4.10 in my Eaton rear end.
On #1, I think that the pumpkin is interchangeable on an HO52 or an HO72 if that helps, but I do not know the answers to your other questions.
On #2, as with others on this forum, I did not know that Eaton used a 4.11 in this rear end until I was educated by this string of posts. As long as the pumpkin is from an Eaton HO52 or HO72 and is going into an HO52 or HO72, is should be a simple bolt in regardless of the gear ratio.
Matt
