The dijit.TooltipDialog is the module to use if you want users to click on/ focus on the content. The content attribute can include HTML, so you could add an HTML link quite easily. Looking at the Dojo help, setting the style attribute may allow you to add scrollbars by setting height/ width.

It may be possible for me to extend this cutom control to allow you to define whether to use the dijit.Tooltip or dijit.TooltipDialog. There are known conflicts between JSF functionality and Dojo dialog functionality, which may mean it's not feasible. I'll do some investigation, but other projects may mean it takes a week or two. I'll add an update here once I know more.