1) Glad to hear you resolved this one.
2) Using PayPal Standard, the order is stored in the database when the checkout form posts to the confirm page. If you where to use PayPal Payments pro, the prder would be stored in the database when the order is confirmed.
3) The only way to delete the tables from the database is to use a MySQL GUI Tool like phpMyAdmin
4) If you are using Paypal Payments pro, the email is sent after the transaction is processed through paypal. Using PayPal standard, the email is generated by paypal.
5) on the eCart support page are tutorials for adding registration to the eCart checkout process: