I have a form that I intent to have users in and out of until they finalize it.

For example:

End user creates new item.  Only has a few of the fields' information required to fully submit.  User saves the form - it is incomplete for final submission.  They come back with the remaining information - update the form - and then can finally submit to kick off workflow.

All the while the user is saving the form by selecting the save button.  Once the form is ready for final submission, there is a YES/NO check box titled FINAL SUBMIT.  The user needs to select that checkbox then select the save button to kickoff the workflow.

Once that is done, I do not want the user to be able to come back to the form and make any modifications.  Nor do I want them to uncheck the FINAL SUBMIT box. 

I'm trying to use the disable rule funtion but it's not working at all how I need it to. 

A) Is this possible?

B) Is the way I'm approaching it accurate?

C) Is there another angle that I should be approaching this from?