1) Fels is definitely oriented towards government and nonprofit mgt. (Fels offers a certificate in nonprofit administration as well). If you were interested in international policy/international affairs type programs then Fels wouldn't be a good choice for you. Since you are interested in nonprofit management, curriculum/concentration wise Fels is as good as (if not better than) your other options.
2) Have you tried reaching out to people who work in the nonprofit sector (specifically the type of organizations that you want to work for) and getting a sense of how much the Penn name will help you in your career?
3) Penn is definitely nationally recognized whereas UW and USC have very good local recognition. I think Penn would provide you better geographical mobility.
4) Since UW didn't offer you any money and you aren't too excited about UConn, I think your decision is between USC and Fels. You need to figure out exactly how much more expensive Fels is going to be and what that would mean for your loan payments. If the Fels/Penn name, the opportunity to take classes at other reputed graduate programs throughout Penn, the personal (small program size ~35 full time students per year) and practical nature of the program, and strong national Penn alumni network (as opposed to USC's local network) will help you improve your career prospects then Fels might be a better option for you, otherwise as they say- follow the money.
Hope this is helpful.