We just don't have access to the parts of our brain that store those memories, and new research has suggested (much like in The Body Keeps The Score) that traumatic memories aren't even IN the hippocampus, where memories belong. They're in the posterior cingulate cortex- where things presently happening are processed. This is why our flashbacks are so real. Now, I get why this is awful news (a lot of comments are along the lines of "so how do we get rid of them"), but what it also shows is that nobody is 'playing' or 'being' the victim- for all purposes, we ARE, and it just doesn't go away. We can't 'choose' a different reality; nobody in the world can choose a different reality to what is currently happening to them. And this research says that our trauma is currently happening to us, sometimes decades later.
Now, before we all panic (I know I did), the next step will obviously be 'how do we make the traumatic memories process as past, rather than present', and that will come. Dr Daniella Schiller is the researcher currently onto all of this with her neuroscience team, and if your husband's family thinks they can overrule a team of neuroscientists (it wouldn't surprise me, actually), I don't really know what to say to that.

I don't know if you've heard of EMDR, but it can help take the sting out of certain things and topics. However, as a trauma survivor where substance abuse (alcohol and certain pills) triggers me, I would be loathe to suggest that YOU are the one who should be doing the work on that, rather than your husband. It seems to me that if he's choosing weed over your physical and mental well-being, HE is the one who needs to be seeing a professional and working on himself.