1. Using the CIFS interface (shared drive) to Alfresco you can use any editor, including Dreamweaver.
2. We use SVN for our source code repo - not quite sure what you mean by the question.
3. Assuming you mean the WCM form output or output from any template running against the DM, then the answer is "yes" if you write the forms/templates appropriately. Our web-client UI application needs more work to be 508 compliant itself.
4. We have an RSS template that can output feeds from the repo on changes to documents etc. You can add any content to the repo itself…
Hope this helps,
Kevin