Does my divulging my mother's old secret, which is her going to the fortuneteller, and my regret for that, along with my mother's repentance, warrant all this feeling of guilt and thoughts of suicide?

As long as you have repented and regretted revealing the secret, there is no justification for the excessive anxiety and fear that led you to contemplate suicide. Fear Allah, turn away from these whisperings, and seek Allah's help. If you are able to seek your mother's forgiveness and ask her to pardon you, then do so. But if you fear corruption resulting from that, then your repentance and seeking forgiveness are sufficient for you.