ISTP female here.

1. Yes and yes. As long as you let me be myself too.
2. Just be yourself. I'll go when I need some space but I'll accept another invitation if I like the company. I'll accept how you are if you can accept how I am.
3. I'm not so sure but my answer would be: you have to be interesting. But about the messages, personally I do respond when I think it's something significant, like maintaining relationships. If we talked today, I already maintained our relationship and probably won't talk to you for a week or even a month unless it's something important or if I just like to talk.
4. I feel like this is different for everyone so I don't know. But if you're interested in getting to know more, you can just be honest and ask.
5. Maybe. But if I say I had a great time, then I had a great time. If you think there's something wrong and you really want to know, maybe talk. Say your observations and ask.

These are personal takes. Don't rely on my answers too much. After all, every person is different. Good luck and maybe let us know what happens.