I also advise against an MSW or a Master's Degree. It sounds like you have great research experience and a great GPA,so I am not sure a Master's degree will help much. The one thing you can do to greatly improve your chances is to get your GRE scores above 160. IMO, your GRE scores are good but not good enough for PhD programs. Also, did you have faculty/graduate students look over your personal statements? These can make or break an application.
Try to get research experience in the field that you are interested in and apply again next year. Do not get a Master's degree if your goal is a PhD program. I think that it will be a waste of money in your particular situation.