You appear to be using the same class to define both a JSF backing bean and a ReST controller.
I'm not sure that's going to work very well and at a minimum it's an ugly thing to compound two such different characteristics into a single POJO.
I have done JSF apps that use ReST, but ReST is not handled by the JSF Controller
Servlet, it's handled by the ReST dispatcher servlet. You can't have both active at the same time handling the same URL request.
The onlt difference between the SelectItem and SelectItems is that SelectItem represents a single entry in your selection and SelectItems provide a list/array of SelectItem. SelectItem itself exists because the controls that use it require a pair of properties (name and value) and therefore a simple generic POJO wouldn't guarantee that. Though these days there are some shortcuts.
You can have as many SelectItem and SelectItem elements for a selection control as you like.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.