SystemSettings and LoggedInRegularUser is always in the context. Your own BO:s are not*.
If you want to display the value of an attribute of a single row from a “normal” BO, I think the easiest way is to create a peer relationship between SystemSettings (or RegularUser) and your BO. Then create a shortcut. Then make an update rule or process that inserts the correct row based on your criteria. Then edit your custom html so that it points to your shortcut. It will work because SystemSettings and LoggedInRegularUser is in the context.
*If you have made your own user BO, you can use LoggedInSystemUser to address them aswell.