Start level and end level are the same. Use that to render a specific level. Experiment a bit. After that it's all about positioning the new menu module instance in your template.

That's correct. The menu module (which is a "core" Joomla module) fetches data from Joomla menus. You tell it WHICH menu to load and then you filter it by menu-level. Just try it.

You are either doing something wrong, or you haven't understood yet the concept of rendering specific menu levels.

In any case, this is no longer a K2 issue but rather a Joomla issue so I advise you to seek further assistance to the main Joomla forum.