There's the pretty clear --exclude option that you can look up for the second question
In answer to the first, I suspect the answer is not easily, but let me see if I understand what you mean. If this is your structure
you want to tar file_1, file_2 and file_3 (but not as directory/file_3)
What you'd need to do is some form of loop through and sub-directories using -C and --no-recursion while concatonating files to the tarball. However if file_3 was also called file_2 I think you'll have some issues.
If you mean that you just want to tar file_1 and file_2, then --no-recursion should get you there.
Note that tar wants to include the path from where you start unless you use -C