I have faced such scenarios so let me see if I can explain this to you. While running a REST wizard it shows a NullPointerException which causes the Rest Data Source Wizard to halt rule creation and revert all changes. The REST Integration wizard, while creation of rules, is incorrectly attempting to use the undefined value of a property, leading to a NullPointerException. This might be one of the reasons for the issues you see. Manual creation of the service package, service method and activity is the best practice and this will let you know exactly, the rules and the how-to's that you create as opposed to the rules that the wizard creates for you.
I hope this information helps you and please let me know if you have more questions.