You can use one single class for static pages (and use one method for each page).
You can use the same one to load dynamic pages, but it is better IMO to load them with a separate class. It will be easier to maintain later.
Using common code: You can always override the CI_Controller with your own, and instantiating controllers from yours. Here is an example about how to do it.
You can load multiple views in a single controller function. A view doesn't have to be a full html document. You can also load the same view multiple times (for example in a loop).
Best practices: CodeIgniter is an MVC framework. IMO, MVC is a best practice. Always use the framework's documented features if they are suitable for what you want to achieve (CodeIgniter's documentation is very good. That link is momentarily offline, so please try this one).