Go to design mode Click on Edit for that parsys and select the component you want author should be able to add

Did you create package from your machine or which machine?Check error.log when installing package

Did you added filters on your package?What all filters were added?

You can use<cq:include path="path to your component node" resourceType="script that will render the componet example [1]" />[1] apps/project/component/text

You can use OOTB reference component, drag this component where you want to refer previous author componentTake a look @ https://docs.adobe.com/docs/en/cq/5-6/wcm/default_components.html#Reference

Take a look @ http://conexiogroup.com/aem-ajax-pagination-using-the-sightly-list-component/It uses sightly JS which executes in server sideIn simple terms you can make ajax calls to your servlet which will return you data based on which page are on.

1. Make sure you have replicate your code ( including component and OSGI bundle) to publish2. Activate your video from DAM 

1. Check the value of property name2. Make sure you are using same value in JSP to get data of pathfield3. Ensure that updated pathfield value in getting stored in JCR

Check these two articles where use can select root path for tagshttp://experience-aem.blogspot.in/2015/02/aem-6-sp2-classic-ui-tags-widget-show-sub-folders-as-namespaces.htmlhttp://experience-aem.blogspot.in/2015/05/aem-61-touch-ui-multiple-root-paths-in-tags-picker.html

Take a look article similar @ http://adobeaemclub.com/multifield-touch-ui-sightly-component/