No restrictions per user

Thanks for this plugin which is almost perfect.
Unfortunately, it suffers from a few bugs:
1- There are no restrictions per user. It would be enough to put automatically in the discount code the email address of the buyer. (“Permitted e-mails” field in the “Restriction of use” tab).
Indeed, anyone can use the discount code.

2- The plugin generates undesirable characters in the email message and in particular HTML tags. like <p>

3- The image or logo is not displayed in the email sent.