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1.) What is the best way to get the prior potential employers to tell me what they were told? Can they be forced to tell me?
If they're public employers, try to FOIA the information from them. Otherwise, you would probably have to depose them as part of a lawsuit.

Quote Quoting Faith
2.) Is there a Michigan company that I can hire to do a reference check for me to learn what they are saying or what questions they are being "silent" to?
I've seen such companies advertised (although I'm recalling national services), but I don't know of any specific companies.

Quote Quoting Faith
3.) Is there a lawyer in Michigan who has dealt with this specific type of retaliation (as it is tricky to prove)? I need someone who knows what these companies could be doing and prove my case based on experience.
Have you tried consulting the lawyer who helped you with your original lawsuit?