Hi Pippa,
I am very sorry you have been hurt and betrayed by your husband of 41 years. Finding out that your spouse has cheated on you is very traumatic. You will be feeling all kinds of challenging emotions and that is very normal. Please be kind and gentle with yourself. The healing process can take awhile with lots of ups and downs, but eventually feels less intense. Many marriages (over half) have gone through infidelity and many couples are able to successfully work though it and stay together. Believe it or not, couples often feel they are closer and stronger having woked through it. There are several different normal stages spouses go through and Michelle's books can help you understand them and when to get professional help. Continue to use this forum to get your feelings out and get support.
I commend you very much on trying to keep calm and being pleasant and not asking any questions. I'm sure this is not easy to do. It sounds like your husband is sharing his feelings with you a little bit and this is a good sign. He is conflicted but at least he is being somewhat honest about what he is feeling and why he is torn. Try to pay attention to what makes the conversations go better as well as what might make them worse. Try to remember that you and him share a lot of history and this "new" relationship he is having with the other woman can in no way compare to what you and your husband have. Everything is "perfect and heightened" in an affair and it is not reality. In due time, especially with this woman's recent loss and neediness, things between them will likely crumble. Try to stay strong and take good care of yourself both emotionally and physically.
It is often helpful to contain discussions about the affair to limited period of times each day so that you are not making all your interactions with your husband so negative and blaming. It is also really tempting to "spy" on your partner. Do NOT do this. It will drive you crazy and probably drive him away. I know it's hard, but try to focus on presenting yourself in the best way possible to your husband. Your actions, positive or negative, will be noticed by your husband. So try to make them as positive as you can, in light of what has happened. I'm not saying to pretend you are not affected, but huge emotional, angry outbursts will complicate things. You need to get this out right now in a different way. Keep yourself active, exercise when you can, go for walks and talk out loud if that helps and do some other activities that you enjoy. It's okay (and good for you ) to have moments where you are enjoying yourself and feel some relief and happiness (healthy ones). Whenever possible, talk to your husband about the positive memories you have with him and the future you want to have with him. Hang in there!!