1. Your punctuation and grammar is nearly flawless. I was only able to find a few mistakes here and there, and they were very minor. With dialogue you can get away with a lot more than in the regular sections of the text.
I am sorry to hear that story and about how it put you off writing. I think you are quite a talented writer, and I can only imagine where you would be if it hadn't put you off of writing.
2. In the majority of the game, Steel's dialogue is essentially what you have: You ask his thoughts on Esbeth's other residents. Or: You tell him you were quite pleased with the meal. Etc. Without quotation marks.
I think it was purposefully done this way so that the player can more easily put themselves into Steele's shoes. However, I have read other documents where people don't do that, where they instead give Steele actual dialogue.
3. Being Canadian I am more familiar with British English as well, so those things often easily slip past me. I haven't encountered anything like that in your document, but that could also be me missing it out of habit too.
4. The only time it becomes kind of, too much, is during the scene when he turns down the player for sex. At least for me. I am sure other people will have different opinions. I know some people don't like it when you actually write how they speak with the accent into the dialogue, rather than just using: 'he says in his lilting Irish accent.' Got that mostly out of this thread:
https://forum.fenoxo.com/threads/code-name-irelaid-suspended.10614/
Edit: Is it bad that I imagine him talking with Miles O'Brien's voice (from Star Trek)?