I don't consider myself to be the average freelancer. Due to my marketing skills. Still, I will talk about the specifics you asked about.
1. I do take more than one project at a time. Usually one big (more than a month's work), and one small ( less than a month's work). I have no problem meeting deadlines.
2. Depends, and is negotiable. I will say that my rates a a hair under average for California. I do this because I work remotely and avoid flying in (but will do it if I have to).
3. I am an American doing remote work from the Caribbean.
The biggest issue freelancers have is that most don't know how to properly market themselves. They tend to think that an ad on HN will be enough to bring in high six figures (it won't). You have to have a good marketing system going on for you. After many requests from other freelancers, I'm about to offer such a system. But its has not launched yet. If you want to know more, just send me an email. The system is built around getting good leads from different boards, email marketing, and content marketing. It took me to almost broke, to , well, a very, very nice place in about 7 months. Anyhow, just email me. Others, keep posted for the launch.