1) Unfortunately, I do not have data on conversion loss for that.
2) It depends of the importance of what you enter your email for. Having to type your email twice is not a good UX. Plus, many people will simply copy-paste the first email field into the second, making the "confirm email" field rather useless.
3) My recommendation would to NOT put a second email field but to always send a confirmation email when interacting with a user's email. And also notice him, after he clicked on the "Register/Subscribe" button that "We just sent you an email to [his email address here] to confirm that you are correctly subscribed/registered". And maybe telling him to check his spam folder if he can't see his email.
Sending an email saying makes it 100% sure that the process worked and the user has entered his correct email and will receive your newsletter.
Another positive side-effect point of sending a confirmation email is to prevent someone from subscribing other people. They will receive a mail saying that they subscribed to a newsletter that they didn't subscribed to and they can then click a link in your email to unsubscribe, preventing having further unwanted emails.
You can also provide more details about when and where the subscription was made, so the user know if it was voluntary or not.