Hello Ousaima,
this is another lively example on how you can already practice META-Health and apply Salutogenesis with your family. Thank you!
What I need to mention is that pain as a symptom is special, and it does not explicitly tell you about phases. Let me explain this way: pain is there for a reason, in the musculoskeletal system it tells you that this place needs  good conditions to heal, and also some time, which the afflicted structure needs to build back up after we reached a conflict resolution. 
But the pain itself is also a stressor by its own, which prevents the feeling of safety we want to heal fast and smoothly. So here we can have two layers of "phases", one may be a repair phase that includes some pain (like after you sprained an ankle) and the other is the stress by this pain, which also leads to further self-devaluation.
And what you succeeded in is to take the major factor for the pain away by finding his conflict themes, the instability and the lack of support by the boss.
You also suggested META-meanings for him: "your stability will never be affected by a person because the power is inside you and that’s what will stabilize you".
Now he wants to integrate this wisdom into his life, and change his thinking/feeling/reacting habits. And this will facilitate his back to grow strong and balanced so that it won't lead to any pain anymore.
About megalomania, this is a constellation which doesn't apply here. We'll talk about these when we deepen the cerebral medulla programs.