Hi,
In case your problem is, the workitem is being sent to the approver in SWI1 in all the cases mentioned then routing to UWL inbox is not handled in correct way. And since the workflow is custom, if the dialog task is custom then it has to be registered in SWFVISU for WD java based MSS.
And the in standard leave request workflow, only single level of approval is possible. In case you are intended for multiple levels of approval refer to the following post:
http://scn.sap.com/thread/1680809
Regards,
Rahul Kulkarni