I think that his wife dieing slowly, isn't really a traumatic event as such, more a life event. The initial event is what is causing his trauma, and because he has never healed from that actual event, regardless the highs and lows, any exposure to normal life events will collapse him, as it will all of us. Think about it like this I guess, in that when a person without PTSD losing a loved one, they can hit bottom, but the difference is they can recover with support quite quickly, and a little time will see them moving forward again without incidence again. Because he has PTSD from an initial traumatic event, and never healed that, add another life event into the equation, and now he not only has watched his wife die slowly, but also never spoken about it, got support he needed, grieved properly, etc etc, thus because of his PTSD, all the feelings and emotions from this other event will be sitting inside of him also, building up with his trauma, fueling PTSD as such.
Because he has PTSD from the initial event, this means he has two jobs too do. Firstly he must heal the trauma, which I think his friend could help him with quite substantially, the second is now learn how to control and manage PTSD itself, which is a whole nother kettle of fish, so to speak. Because he would have bottled up everything in regard to his wife dieing gradually, all this would also need to come out, otherwise it will continue to fuel PTSD.
Think of it as PTSD is the fire, and without fuel and air, fire cannot burn. Air is life, which is a constant. Stressors within life come and go, they are fuel. So air is always present, so all PTSD (the fire) needs is fuel to burn. Any life stressors that are not dealt with immediatly will cause the fire to burn. Once the fire burns (PTSD), it is not just as simple as smothering the fire to put it out, instead it must be resolved, discussed, argued even, and dealt with emotionally to extinguish the fire as such, being PTSD.
If you think of life with PTSD like that, then what you must do to help your BF, is to extinguish all the stressors, emotions, etc etc that he has been exposed too in life, and the only way to do that is to get them all out in the open, look at them rationally, discuss them, analyse them, get emotive about them. I say emotive, because he will say he is angry, yet anger is not an emotion, it is an emotional response to an emotion. What he is trying to say, is he is frustrated, hurt, etc etc, which are the emotions causing anger. Dealing and coming to terms with emotions then stops the anger. So this in essence would help him to lessen the fuel as such. Even though when dealing with issues, the response may be a big burst of fuel to really get the fire going, its a burst that is required to burn all that internal suffering, then nothing is left, so the fire calms once again, except with less fuel present now. Each time you get your BF to get to the emotional level, this cycle will continue, thus eventually all his fuel is gone, which means the fire can no longer burn, as life itself is not enough to create fire, it must have fuel (stressor) to allow the fire (PTSD) to burn once again.
Basically, if he starts at the initial trauma, his fire will burn large for a while, then reduce, then deal with the lose of his wife and issues involved in watching her die slowly, the fire will burn large once again, then die down, and so forth for each event within his life. At that point, then learning how to manage PTSD might come a bit easier as such. I think the exposure to his friend could start the process though.
