Dear friend, I am still on it but I can help you to try the following:
For the textToSpeech
- Use the API of ReadSpeaker https://www.readspeaker.ai/unity-unreal-game-engine-plugin-free-trial/
or - Use the API Metahuman SDK. MetaHuman SDK in Code Plugins - UE Marketplace
For the Connection to OpenAI
- Use directly the OpenAI API. OpenAI API
or - Use the OpenAI API plugin from KellanM. GitHub - KellanM/OpenAI-Api-Unreal: Integration for the OpenAI Api in Unreal Engine
I hope this help while I can make the video.