Q1 - AFAIK comics don't have designated covers.
Before I add it to calibre, I ensure first image in the zip (which what I always want as cover) sorts to the top - often by naming it as something like
!cover.jpg.
Q2 - when adding comics (as ZIPs) I get author and title from the file name
Q3 - Use a Custom Column, something like
Q4 - No - again use a Custom Columns, something like
BR