In APA Style, “et al.” is the only format for abbreviating citations. Consistent use of this format, detailed on pages 174–178 of the Manual, prevents any misreading or confusion about the citations. Because it is so important to acknowledge the ideas and works of others, precision and consistency are essential in the presentation of citations.
For your question on running heads, yes they should be to the left in APA Style. You can find examples of in this sample paper: http://www.apastyle.org/manual/related/sample-experiment-paper-1.pdf
Note that the requirements for classroom assignments and other types of publications sometimes vary from APA Style guidelines. Schools often publish their own guidelines for dissertations and theses, which often modify APA Style guidelines.
Finally, if you have other questions about specific applications of APA Style, you may want to e-mail styleexpert@apastyle.org
Use "et al." only. Remember the styleexpert e-mail address.
