"Since the real reason for our acting out is excessive lusting, why isn't that our main focus (as opposed to just 'not acting out')?"
And if it is part of my focus then what? I don't make it go away by the power of my focus anyway! I haven't that power! I just surrender the right to lust today and do the best I can to stay interested in Hashem, and in my job. So I lust sometimes, tsk, tsk. I have a besmirched record. Shame on me. But I will do what is in my power to remain sober today, at all costs. My perfection is not the issue, but my honesty. I can be honest without being perfect, as long as I am honest about my imperfection.
"And what would you say about an issue that is purely emotional, such as hating, jealousy or fantasies and lusting? There, the action is actually in your head!"
I have really found it to be true that "I cannot think myself into right living - I can only live myself into right thinking". The mess in my heart is not always in my power to change. I can admit and share it, work steps 4-9 on it, but in the end, the 7th step only works if I let go of the jealousies, fears, entitlements and resentments that affect me and sincerely ask to Hashem to wash it all out of me.
The way this "character development thing" has worked for me thus far is this: My own acting out has taught me that I need to be sober. No negotiation, it's #1 before my wife, kids, and my own feelings. But I have character defects of Pride, fear, entitlement, grandiose thinking, and resentment that get in the way. They make me very uncomfortable, and if I get uncomfortable enough, I have accepted that it will lead me to act out for relief. Not losing my sobriety motivates me to work steps 4-9 as needed, in order to remain sober and not lose everything and die. That's also why my entire avodah has grown over the years. I feel this connection is needed, and I do whatever is necessary to grow and maintain it. Not because it's right, but for my own good. If this is horrifying to some, I have nothing to say except that it is how I understand ani leDodi v'Dodi li - He want us to accept Him, but "accepting" Him also means to use Him! Dodi li means he is for me! Use His Power!