It's not that the cuddling is triggering specifically - my PTSD is not related to abuse or anything like that - it's that people with PTSD often get completely over whelmed by noise, touch, sensations basically. It's similar to the sensory overload autistic people can get. It's like everything's coming at you, and you can't bear one added sensation. You risk lashing out verbally or physically. I think I turn to CV exercise when I'm getting towards that state, it helps get rid of a sort of nervous tension. Other times I love a hug, but DH knows to read me first.
The other thing I do to chill is I've rediscovered writing fiction. It gets me in the right zone, almost drugged. Playing music works sometimes but not if I've reached the kind of state described above.
Sleeping is tricky too - I have to 'trick' myself to sleep by reading until I can't keep my eyes open, as I can't lie there and try to fall asleep, as that just means all the thoughts, flashbacks etc crowd in. I still, despite a lot of treatment, sleep better during the day, than during the night. It feels safer. My night-time reading drives DH mad.
I hope your DP is having proper, decent PTSD treatment like EMDR? If he's had PTSD a long time, look into it again as 10+ years ago EMDR wasn't typically used, tended to be more CBT which seems to help get a level of functioning back, but not as well as EMDR, which is now a NICE-recommended treatment.
You also need emotional support, try counselling maybe, or calling one of the PTSD helplines.