Okay, I will take a shot at this.
I am a recent Grad (within the last 3 years) with a double major in history and econ., minor in pol. sci. LSAC does not focus that closely on your GPA for your major or minor, they focus more on your overall GPA. Switching your minor will not impact this.
I would recommend that you finish up your econ major and double major. This may slightly be beneficial for Law School (I think there are some threads on this, see http://www.lawschooldiscussion.org/prelaw/index.php/topic,515.0.html
), but it will definately be valuable if you are interested in public policy/leg. practic/gov't relations. Additionally, it is more 'pratical' then Pol. Sci. and may help you get a job out of college. It is only one more semester/quarter, so just do it unless there are money/other issues.
I would recommend that you do the internship and tutor, any resume boosters are a good thing for law school regardless of whether they are related to law or not.
One suggestion, if you are interested in Public policy/legislative practice/government relations you should look into Masters and PhD programs. You 'could' focus on this at law school, but it would be cheaper (and perhaps more interesting to you) to go to grad school for this. Normally, schools pay you to be in grad school (TA, etc.), law schools don't. The issue for public policy/gov't relations with most Law school programs is they focus on the law, not government/public policy so much (unless you go to georgetown or somewhere like that). Just a thought. Anyone else have comments on this?
Hope this helps.