Hi and welcome,
Only a few details to start from but I will try to offer a few tips from my own experiences.
Regarding PTSD:
Discussing your PTSD symptoms can be very helpful but it can also stimulate flashbacks, sometimes it seems like a double edged sword.
Try not to force answers from your boy friend, I believe it's best to take your time and listen if he decides to talk about it but let him dictate the pace and how much detail to reveal.
Ask your boy friend if you can accompany him to his Psychiatrist, but don't be offended if he doesn't want you there at first (he may believe it's the best thing to do). Just letting him know your there for him if he wishes can be all the words he needs for reassurance from yourself.
You've already started using the Internet to learn more about his conditions. At times I feel the more I learn the more complicated it can seem but don't let it stop you trying.
An article appeared several months ago in the news regarding computer games being helpful for Combat PTSD. At this time I can't find that specific link but try browsing the Internet for
"playing Tetris may reduce flashbacks" for more details.
Regarding his dementia:
I'm sure you're already aware that there are dedicated websites to dementia but here are a few things I've read in the news recently that may be of some use.
Keeping the mind occupied; socializing with people, hobbies etc.
Apparently gardening may extend and give a better quality of life, also it can be helpful for people with PTSD to.
People with dementia can often wonder off and as you've unfortunately already experienced also become lost.
If he usually carries a mobile phone check to see if it has GPS; if so you can probably enable it and then use a PC at home to track his location if needed. If he loses his mobile phone there maybe other GPS devices available that can also do this (please see details below).
I hope this information is of some benefit to you.
