how to make config fields stick at admin/structure/types/manage/?
You can add a custom submit handler for your custom group of options and controls. For example on the base form you add an additional #submit value and check your own custom fields:

$form['#submit'][] = array('mymodule_form_followbtn_custom_submit');


if needed you can validate is form element independantley:

$form['followbtn']['followbtn_default_mode']['#element_validate'] = 'mymodule_followbtn_element_validate_default_mode';


or ...

$form['followbtn']['comment'] = 'mymodule_followbtn)element_validate_comment';


Then your submit function just does your processing (after elements validate on submission:

function mymodule_form_followbtn_custom_submit($form, &amp;$form_state) {
  // save your stuff ...
}