Hello, for all of you who struggle with understanding the character arc or have trouble plotting it out, I want to share my step-by-step character arc technique.
Since a character's personality is only a response to the outside world they live in, I've developed a questionnaire including the outside world as much as the inner world of the character, because they go side by side, and a character cannot change without experiencing a change in the outside world first.
I've taken the original character arc questions and rephrased them, so that they are easier to understand and give you enough space to brainstorm to avoid getting stuck.
Here they come:

1. The core of their problems that's left the most traumatic mark on their psyche:
2. a) The way it affects their external life:
2. b) The way it affects their internal life:
3. a) An external change they desire to be happy:
3. b) An internal change they desire to be happy:
4. An obstacle standing in their way:
5. The reason why pursuing their desire became possible:
6. The reason for still being discontent after overcoming the obstacle:
7. A new desire, more concrete and attainable:
8. The course of action necessary to reach what they desire:
9. The fear they need to conquer/the thing they need to sacrifice:
10. a) Their external world after getting what they desire:
10. b) Their internal world after getting what they desire:

1=backstory
3=misbelief
5=catalyst
7=need
9=fear

I hope it's helpful. I wish you good luck with your story.

There's a lot in what you say.  I imagine most successful writers cover many of these points, instinctively if not deliberately.

The only issue I have with tick-box exercises is that the people who use them tend to let the mechanics show; which is the death of all spontaneity.  The same is true of writing too detailed a precis before the fact, and doing your research before writing your first draft.  In each case, the danger is that the material will start steering the writer instead of the other way round.

Perhaps the best approach is to produce a guide for yourself, read it before starting - and if necessary at any point where you get stuck - and then leave it out of sight in a locked drawer. 

As Jo says, in different words, the danger is that the writer following this list too thoroughly becomes more of filing clerk for the character's psyche and less of a storyteller.

Sometimes I have no conscious idea what makes my characters tick until they've revealed themselves through their actions and reactions on the page.

This is why they can still surprise me.

Gyppo