1. You need to be clear and concise. I got about half way through your narrative without hitting anything relevant to this question, and I gave up.

2. He doesn't have any evidence that the allegation is what's causing his difficulty getting a job. If he thinks he has grounds to sue his former employer, he can get a free consultation with a plaintiff-side employment lawyer.

3. Sometimes there's no one else to investigate.

4. You mean, can he lie in interviews or on job applications? That's never a good idea.