Thanks for the feedback so far. I'm going to try and answer some of the questions that were posted.
Yes, we married in our early 30's and it was the first marriage for both of us.
I don't know what "age related sarcopenia" is but I'll look it up and check it out. Running is the only thing she's really enjoyed in terms of exercise, which is somewhat annoying to me, because in the winter if she can't run outside she does nothing. She refused to even run on a treadmill. Then she's grumpy with an even lower self-esteem. I think the low SE is at the center of many things though. She could get good at so many different athletic activities if she wanted (weightlifting, cycling, swimming, yoga, pilates, etc.), but I think she's afraid of how she'll look, what others will think, etc.
I would not say my wife was promiscuous as a teen, though she lost her virginity at 15. I'm really not sure how much she got around after that, but I don't think too much until college years. She's still somewhat closed off with me though about her promiscuity. I was 19 when I lost my virginity and probably only had 5 or 5 partner altogether before her.
I wouldn't say women hit on me a lot, or ever have. I'm an attractive guy. I have a 6-pack (sometimes just a 4-pack in the winter months

), exercise 5 times per week, eat well, have all my hair, etc. I don't have my measurements, but I'm not overweight or underweight. I am short, so that I think has sometimes kept me from standing out in terms of attracting women superficially. I consider myself intelligent, caring, pretty darn funny/witty and easy to get along with. I'm probably more of a "beta" guy, though the more I'm reading here and elsewhere that is probably something I need to work on. I figured I was safe to be a "nice guy" once the wedding vows were taken, but apparently not? Yes, I dress nice. Not over the top flashy, but I like to look good on a consistent basis. I'm a 39-year-old professional, so I think it's important to not look like a slacker.
Yes, it was a gang rape, not a gang bang. She did not want to do it, but as she describes it, she put herself into an unsafe situation with a bunch of idiot guys and she was very intoxicated. No excuse for those guys, but I think she's just trying to acknowledge her mistakes as well in the whole thing.
My "impure thoughts" have to do with ideas of having an affair and things like that. Not usually so much sexual, though that's part of it, but mostly I think because I'd like to be with someone that I feel admires, respects and is attracted to me. My wife doesn't show much interest in those ways lately, so there have been many times my mind has wandered into thinking about what life would be like with someone else. It's probably more about feeling lonely than anything else.
According to her, it's not specifically me that doesn't do it for her, she just has a low sex-drive. She doesn't fantasize about other men, doesn't masturbate when I'm not around, doesn't think about sex, etc. She tells me she thinks I'm attractive, but just doesn't feel very sexual. When she did individual counseling there was some focus on that, but I'm not sure it did much ago. Of course, I think that also had to do with my wife not wanting to pursue the ways in which she could improve that part of her life. She just didn't want me to be miserable, I think, instead of wanting to improve the quality of her own life in that way.
To tell the truth, I can't say for sure that she doesn't fake orgasms. We did some work on this during therapy, based upon some direction we were given to spend time just touching each other and discovering what we like and communicating with each other. She tells me she's been able to achieve O now when I rub her clitoris rather aggressively, and it would seem that is the case. If she's acting she's become really good! Then again though, she faked before some who am I to judge? It's certainly an area of distrust for me. But...that's probably not my major issue anyway. I just want us to work on having more of a spark in our sexual relationship.
Like I said before, I think if anything I've been overly-attentive to her needs, wishes and desires (or lack thereof, I guess). I've tried about every avenue I can think of when it comes to romance, creativity, acts of service, etc.
I think a really big frustration for me right now is her continued lack of respect of my need for a deeper level physical connection to her. Many things she described as needs over this past year I've met full on. Helping with kids more, cleaning, family fun nights, going out on date nights more, etc. If I said what she seems to be saying, which is, "Oh, I don't really enjoy those things, so I'll step it up a bit for you by about 50%, but don't expect me to really get into it." she'd be furious with me. Yet, that is how she responds to my sexual needs. She makes it a point to try and have sex once per week, but there is very little newness or fun about it. Does that make sense?
I have a friend who has had affairs and makes the point to tell me that he always just does the minimum in his marriage, because otherwise his wife EXPECTS and gets spoiled by all those special things he does. Plus, he said when had the affairs and it came out to his wife that it was a hugh wake up call to her to start taking matters into her own hands (so to speak). She acknowledged that she was not taking care of his needs and things began to improve in that area. Of course, there were many other problems that came about as a result of the affair.
Of course, I'm not trying to convince myself, or have my friend convince, to go have an affair to improve my marriage, but the theory makes some sense to me. Maybe I do work too hard and worry too much about our marriage and need to back way off on that. Maybe it's time for her to start fighting for us instead of me?
More thoughts?
I do appreciate the suggestions that have been offered so far.