1. CMIS exposes a REST Atom feeds binding so you can use Apache Abdera Client to parse atom feeds from a Java application.
Abdera allows you to invoke standard HTTP requests and methods needed for CMIS operations (GET,POST,PUT,DELETE).
Now there is a new Apache project, Apache Chemistry, that it will provide us the standard implementations of CMIS client for REST and Web Service binding.
2. To manage your own custom content types with custom properties you need to use Alfresco 3.2.
3. I think that REST is much better and more easier to implement than WS binding
Hope this helps.