First of all, I understand your hesitation. I remember when I first started privacy and giving out personal info was an issue with me too, and while there are always risks, your info is pretty safe when you use reputable companies. Just always make sure there is a padlock in the lower right of your browser before you give out your credit card info and personal info, etc.
So to answer your questions....
1. Yes you can use your Visa with almost all registrars
2. Most hosts will give you the option of either paying by month or by year
3. Your web hosting company provides the email addresses. So you will setup
yourname@yourdomain.com after you buy a hosting plan
4. As long as you use a major credit card the currency is converted accordingly
5. Almost every company asks for your phone number when you order just in case they need to contact you about your account. I've never had any issues giving out my number