Hello. Here are your answers:
1)You can not configure this, BUT when someone cancels in paypal, they are brought back to your site with a message saying the payment was cancelled. There is a link to \"try again\" which goes back to DT Donate.
2) You can turn on Community Builder integration, then when someone is logged in while donating, the donation is tagged to that user. We also have a CB plugin that shows that user their donation history in their profile.
3) You can customize the message above the form, yes
4) You can create all types of custom fields, so yes you could make a checkbox for this and mark it as required.
5) Yes all fields that are required for a payment are required and marked as such.
6) There is not a captcha system at this time.
I asked all of these questions prior to purchasing since there is no refund after purchase. I quite understand your position as you are selling a digital product, so I have no issues with that.
Yes, this is the right way to buy a component! Ask first! Thanks!