2, clarity and resolution have a relationship with the regular size of the package 300 resolution is sufficient, there is no way to ensure clarity. Set how much is how much. Save as a PDF in accordance with the default option settings on it.
3, I do not know what you said the copy is the content of the package or you design instructions, if it is the content of the package you start to use PS, the copy is also done in PS is not better. If it is the packaging design instructions, where to do it is no problem, even with Word or ppt is no problem.
4, it is recommended to use AI to do, if the complexity of the map or can only use PS to deal with the map, processed and then pulled into the AI is better, remember to pull into the AI need to be copied into a separate layer and then pulled into the picture you need to deal with, or directly open the PDF file in the processing. If you are only responsible for the design, and the design content does not involve the production of later work considerations are less arbitrary design. If you need to produce remember to do a good job of bleed bit, and other pre-press notes.