I am an English teacher, with a Master of Applied Linguistics. I am highly skilled in all areas of English, and can give the following answers to your questions:
1. I have general writing experience on this site, and have written email courses and articles with great success. I am 32 years old myself, so I believe I am more than qualified to help in targeting this age group.
2. I have edited a number of books on this site, each with excellent levels of feedback (and most five-star). You can see these on my profile.
3. I have edited at least one ebook in the self-help genre, and received five-star feedback for this.
4. I am available to complete this job this month, and will have more availability once the school term ends at the end of this week.
5. I am an Australian. We use British English spelling and grammar here in Australia, and I am able to easily check guidelines regarding the Chicago manual of style.
6. If you send me your first chapter, I will have it edited within the next few days, for your perusal.