What are all these missing CiviCRM CSS and jQuery files?
Some of those files should exist in the 4.7.15 filesystem; others shouldn't.  The question is why those files are being called at all.

Most likely, you have an "HTML Snippet" somewhere in Drupal - perhaps a "sign up for our website" block or similar.  HTML snippets really should be removed if possible - but if that's not doable, you should generate a new HTML snippet and replace the older one.  That should cause MOST of these to go away.

The other thing I'm noting is that the jQuery plugins SHOULD load, not 404.  I'd check to see what happens when you visit those links directly.  It could be an HTTPS redirection issue.