I've been contacting a old law employer I did an internship during one semester of school. That person hasn't gotten back to me at all. I have a couple other law employers I can get affidavits from fine. What happens if I can't get it from this person? Do I have to keep nonstop trying until I get it? I don't live near that area anymore so my only contact is phone/email/mail, otherwise I'd just drive over and and try an in person meeting

Yes, you will need it, unless the employment was before you reached 21.