Let it go. It has been some time ago and you should have forgiven him and let this go at the time you took him back. Now you live with him and you are still holding on to this nonsense.
You need to get som help here with your issues cause you have them. If you are still so upset why did you get back with him and move in with him. If you love him and took him back, why are you still upset by this.
You say he has changed but obviously you do not believe it and you do not trust him. So why are you with him and if you want to be with him, why does this matter. It does not and you not being able to let it go after all this time shows that you do not know your own mind.
You are confused and have issues with holding things and not being able to make up or even know your own mind. Get help before you destroy this relationship over nothing.
I have dealt with the same feelings, but in your case it doesn't seem that he had any sexual contact with her. I would just take it a day at a time. Time heals all wounds.
Also jus talk to him about everything.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.