Well gee, no one else has answered your question, so I'm going to to give it a try.
First of all, after reading your whole post I'm going to answer you from the last details first.
It sounds to me like a lot of your preoccupation with her responses is more of a concern about your own abilities to please than anything else. That's o.k., most nice men are like that. However, chances are from what you say that she is quite happy with you, thank you very much.
You mention 40 years of mariage and no more periods, ie; post menopause. Well, if this has been a one orgasm type woman, post menopause is hardly the time to realisticly expect her to start having multiples. First of all, not all women are multi-orgasimic. For some, one good round is is all that's needed, while others with more energy/drive, etc., can have more than one. Either way, keep in mind this is no barometer for a woman's genuine capacity to be enjoying herself.
Secondly, for most women, the clitoris becomes very overly sensitized after a nice vigorous session leading to orgasm, so that further contact there can lead to discomfort. At this time, penetration is most welcome. SHe could be reaching a vaginal orgasm, but different from clitoral and not as intense but wonderful as well. Every woman is different, but the clitoris is the true hot spot for most.
The part about the moaning and groaning or absence of it, may be due to her having a quiet and undemonstrative personality in as well as out of the bedroom. If she was repressed in her upbringing about a number of things, then this would be reflected in her sexual behavior as well. I understand that as a man this may be a turn on for you that you feel is missing, but again, remember that this is not necessarily a reflection of you as a lover, but possibly her own personality.
In any case, menopause is really not the time to start expecting changes of this nature to occur after so many years of established patterns. However, there are things that can help here. One is, an increase in communication between you. Please be careful of how you bring it up to her so that it doesn't sound like you are complaining about being dissatisfied with her, wich would be as destructive as her declaring to you that she thinks you are a poor performer. The idea is to open up the lines of communication in newer and deeper ways, trying unexplored, romantic and safe settings in which to open up about your mutual real feelings.
Secondly, a woman her age can regain her libido and energy, but it requires a little help from some hormone friends. Please read up as much as you can on 'bioavailable hormone therapy' which might be a real help for the two of you.
Please note I'm not suggesting talking to you primary MD for a prescription of harmful synthetic stuff! Do a google search and find out all you can. This should bypass a lot of other stuff and return to you both a quality of experience like in previous years. And who knows, maybe even beter!!
Blessings to you both. :-)