You want to risk paying them 10,000 and then seeing that they are still not releasing your documents as they want the balance 90,000 ?
Look, here on this forum we can advice you on the legality and procedure. We also talk on the ethics and what we should have done. However, the decision and its consequences are entirely on you. If you were paying me for advice, then I would have to see in details all documents and its wording and the impact on all stages. But as the things stand, you have to make your own decision. This forum has given you a lot of feedback on which you can make your choices