The theists I engage with online tend to rather strongly. In real life, I can count on one hand the number of people I'm "out" to (although other than professionally, I'm not particularly hiding) and they're not sharing their assumptions about me or wanting to talk about it.
There are exceptions online though. Some liberal Christians are willing to see me as capable of good morals / ethics / works and some of those actually think that god's grace is active in my life even if I don't believe in him.
Not very often due to the fact that I don't tell people until I've been around them for quite some time at which point they usually figure it out themselves, unless they are the type that really want to talk about religion then I'll reveal it earlier. then have to go through explaining why belief doesn't make you a good person, and if God is the only reason you don't kill and rape people you are a horrible person and me not doing those things without fear of eternal damnation makes my morality better.
Yes. Once I shared I was atheist I was questioned about this.