To login to chat as the broadcaster you need the chat_login scope. Which understandably broadcasters are wary about giving out.
Preferably I’d get the bot modded, but it depends on what the rewards are that you plan to give out.
Don’t need this step you can do this via the extension install flow
Try this: Extensions Reference | Twitch Developers
You’ll be three to five minutes late joining/leaving the stream due to Twitch API Caching