This reply will be brief again Bella, I will be on more in the morning likely. I am up because Evie is ill but I decided to come on here for a minute to answer you. I am glad Evie helped you and Veiled has very good insight, she will be helpful to you I'm certain. From all you are sharing it sounds as though you are trying very hard to do the right thing. Well done for that. Perhaps the only matter you must really work on is patience? Far from easy though, I know that from personal experience. However the PTSD sufferers really do operate on their own timetables, and that is something we as carers need to accept.
I would imagine Christmas would be most difficult for your husband; it is difficult for many here, an added stressor for them. He may have been good in previous years but that is pre-PTSD, correct? I suspect too, it is a time where he may feel pressure to "perform", to be happy, to socialize with others and so forth. Christmas carries many expectations. At least with Evie it is so.
Bella, I know you said you have read many articles on here, however have you read this one:
Understanding PTSD - Edited
It is one of the best articles and explains the stress of PTSD extremely well. If you haven't read it I highly suggest you do. The PTSD Cup Explanation helped Jim and I tremendously in dealing with Evie. It was the first time my husband and I really gained understanding into what she was experiencing and why she reacts the way she does.