Hi Aashi
First of all.... compliments on working on the "Mother of all Workflows" .... I can see that in your screen shots 
..... try using sub-workflows for better modularization next time .... if possible!
So, when the user "Actions" something, then only the WI should end and not by back or by clicking the "confirm" button (in case of 'confirm end of processing').......
When this "Action" happens, is the system generating any event? if no, find an enhancement to trigger your own event....use this event as a terminating event for your step. The terminating event will "tell" the workflow step that the requisite action has been performed....else wait for that to happen.
I know, it will further complicate this "Mother of All workflows" ... however, this is the logical way I can think of (considering that the user does not want to see the ugly little box of 'Confirm End of Processing' and the management does not trust it's users that they will confirm truthfully 
)
Regards,
Modak