Internal external key of the form as a text box

I need to do something very similar to the following SO question; How to create a built-in foreign key feedback formset

Although there is a solution on this, but it doesn't work for me.

When I implement this solution, I get a RelatedObjectDoesNotExist error and the save method starts an infinite loop.

Here is my code; https://dpaste.de/Gkcy#L65,78,79,86,94

I have highlighted the code where I am getting errors.

Can anyone have a peek into this please, this has bothered me for days and yes, I'm new to this :(