The process does proceed even without response from the former spouse. It just makes it more difficult without that testimony. Without the former spouse's testimony, the petitioner really needs some other input, such as witness statements, medical records, etc.
And, there is no substitute for an official declaration of nullity.
However, if the annulment is initially denied, one can appeal to Rome.
Thanks for your prompt answer to my question.
Does that go for all of the Eastern churches who are in communion with the Pope? Melkites, Maronites, Chaldeans, Armenians, Ukrainians and all the rest?
What does "internal forum" mean?