I think that ex-members of abusive churches and cults can get a lot of benefit from knowing hermeneutics. Leaders of abusive churches and cults usually do not teach their members principles and methods of interpretation of the Bible or teach very little. They have some reasons for that. They want their members to closely follow their teachings without any considerations, questions, and doubts. Knowledge of hermeneutics can help ex-members to think using their independent mind and thus be released from their group doctrines.
Leaders of abusive churches and cults often do not have any regular principles of biblical interpretation. Instead of taking the doctrines from the Bible, they twist the Bible in order to support their wrong doctrines. They like to use unclear biblical texts for that. They often use such things as figures of speech, parables, allegories, types, and symbols to give them the meaning they want. Doing that, they violate one of the main principles of biblical hermeneutics - any doctrine should be based only on clear texts of the Bible. Unclear texts can be only illustrations of the doctrines based on the clear texts.
There are also many other principles of hermeneutics that leaders of abusive churches and cults violate. So, the knowledge of biblical hermeneutics can help ex-members to find out the leaders' erroneous interpretations which are often made in order to prove their "God-given authority," the doctrines like complete submission to the leaders, and so on. When these errors are exposed, ex-members will see that the teachings proved by these methods are wrong.
The knowledge of biblical hermeneutics can help ex-members to understand the Bible better and to be released from the necessity to rely on their leaders' interpretation of the Bible.
Abusive churches and cults often have a tendency to pay more attention on the spiritual experience than on the Bible. Independent Bible study can help ex-members to understand their experience better.
Independent Bible study can also help ex-members to find the biblical concept of God. One of the problems is that abusive churches and cults tend to give an impression that God is very cruel. However, the Bible reveals that God is loving. Knowing that can help ex-members in their personal relationship with God.
There are actually many benefits from the knowledge of biblical hermeneutics and application of this knowledge. I do not think that I mentioned all of them.