It depends on other issues, such as will you be suing the attorney. It is best to discuss this with any attorney that you hire on the case against...

No that would not be a conflict of interest.

This would not likely be a viable case. You can now hire another attorney and the former attorney might not be entitled to any fees.

You should request, in writing, that document from the attorney.

You can use another attorney.

Hopefully he appeared. An attorney cannot withdraw without permission from the client or a court order.

One possibility is the State Bar. https://apps.calbar.ca.gov/complaint/Upl/Index

Consult with experienced debt collection defense attorneys in the state where this occurred. Use the Avvo search tool to find an attorney....

They should not be able to get your social security. There might be nothing they can collect so bankruptcy may not be necessary.

If general denials are allowed, that would be appropriate, and include affirmative defenses. A motion of some sort may also be a way to respond.