Hi ferday, chris13,
Honestly, for three and four, I would just select all and first do the "Clean" option from right click > Library Tools.... It will only change those that require it, then you know that everything is correct from then on, and then do the Rename, move and copy tool on the whole lot, using your file path rule, and again, it will only update those that require it.
For #2, careful with jpg vs jpeg. If you have "Tools > Option > File Location > Cover Art > Audio Mode" set to "In same folder as file as Folder.jpg" then again, select the lot, right click > cover art > save cover art to external location specified in options will write any missing Folder.jpg files
As far as I know, #1 can't be done. That "Swag of Tools" kit over in the 3rd party forum might be able to extract the info for you, but, if it can, that thing's way over my head so someone else would need to advise.
The substring search comparing filename path with library fields will work for the most part, but will fail for any cases where illegal characters have been replaced in the filepath with underscores...
-marko