It’s really cool to see how good you’ve gotten at identifying what’s a 9 or 10, and what’s not. You went in to that interview and immediately came out knowing what the real ranking was. A lot of people might have tried to keep the rose-colored glasses on! I’m glad you already have another potential 9 lined up! 🙂
I think that start date, like salary, is probably negotiable. Obviously if 10/10 is ideal for them, they’re going to say so in hopes someone will be able to accommodate them. But for you to want to give your current job at least 2 weeks notice is the respectful thing to do, and a future employer shouldn’t be upset for you treating a past employer with that kind of respect. (And if they DO get demanding or testy about that, then that’s a red flag).
It’s also totally OK to be thinking about all the time you put into your halloween costume. If you get hired and they don’t have a party, maybe you can organize something yourself (at work or outside of work) so that you get to show off your creation!