Hey Rodger,
Coming from your background I have no doubt your digging D8. I'm sure your familiar with Symfony http://symfony.com/ and Twig http://twig.sensiolabs.org/ is pretty big for us front-end guys.
Still, it ain't there yet.
1. D8 tutorials and docs for module developers are pretty sparse. It has been a moving target and your best bet is probably to dive into porting a contrib module (see #2) you find useful. Much of this is still relevant:http://drupalwatchdog.com/volume-4/issue-1/upgrading-your-modules and there are always the Drupal docs https://www.drupal.org/developing/modules/8.
2. This sounds like a classic use of Webform https://www.drupal.org/project/webform, there is a D8 port underway.
3. A simple PayPal or Amazon affiliate link? Aside from that, I can't imagine trying to build an ecommerce system with D8 in its current state.
I have a similar background and share your excitement about D8, but am still starting new projects with D7 and advising clients to do the same. At least until there is a real upgrade path -- and progress on that front isn't spectacular.