Fair player to you mate, i really identified with your post, ive worked with a lot of people who have suffered from PTSD and the gym has been a huge lifesaver, i dont say that glibly i mean literally. It cant just be done when the weather gets better outside it has to become a ritual for psychological and physical homeostasis.
The basis for PTSD as im sure you know, is when you experience trauma, your bodies natural fight and flight responses become overly activated and get way out of a controllable balance. Often when risk is perceived, real or unreal adrenaline is released into your body and a surge of energy is release into the body and the mind, its quite an unbearable experience when you dont have a handle on this. Its only equaled by the deep low of fatigue and depression once its gone. High, Highs and low lows.
What the guy does is something primal, when the flight response is activated and adrenaline surges, its important to work your body up to react to your internal physiological chemical release, in short the gym the gym burns of the adrenaline and regulates it as well as being an outlet for all the psychological experience of trauma that come with PTSD.
I really admire you for posting that experience and advise for people, i heard and seen it so often. PTSD is a horrible and very challenging condition, it doesn't get the recognition of significance it does.
Id be a regular gym goer and just for me i dont get the same holistic benefits out of it as working out as home or outside, mental health wise.