I provided the detail on the first issue in our previous discussions -
A. In the context of the scenario that you describe, air is always present.
B. This is true for any realistic pressure that can be applied by the nurse.
C. This is true for any and all possible sites of bleeding from the nurse.
D. This is true for any and all possible external surfaces of the needle.
E. This is true for any and all possible reasons why a needle may be inserted.
On the second point, I just provided all the detail that is pertinent - the nurse can remove the cap with the fingers in any way that is easiest for the nurse, It is fine to twist, pull, push, etc. Any method that the nurse finds easiest is OK.
The method of removal of the cap has nothing to do with whether nurses prick themselves. Nurses can prick themselves regardless of how the cap is removed. But from the beginning, you have consistently said that the nurse is not pricked in the scenario that you wanted to discuss.