Paint program for MacBook Pro

Mac Basics: Using a scanner - Apple Support

the inherent problem with scanning, especially on cheaper paper like newsprint is the edges can not be outlined clearly and often they come out jagged. You either need to clean them up manually and turn them to line art or see if there is a line art alternate to what you need to scan.

you will likely find more iOS packages for this then you would OS X but what your asking may have a very small niche with this community so the "any one it particular" is going to be your trial and error to determine.

http://www.matchwoodstudio.com/sketchpen

You should look for one on the App Store.

I could not tell you. Never tried any. But there are a lot of them. You can also search at MacUpdate.