One thing that you might consider; women loose testosterone as they age.
A woman's testosterone levels are highest in the early twenties.
The ovaries produce testosterone as well as estrogen. We can loose our sex drive and loose the added benefits of the hormone. The hormone affects sex drive as well as energy levels and general sense of well-being.
Even if your wife is interested in sex, the lack of testosterone can also mean less physiological reactions that are seen in the genitals when she is aroused.
Now they have simple patches (like the stop smoking type) that she would put on the abdomen or buttock and the medication is absorbed. Oral meds can be too much of a strain on the liver -and raises 'bad' cholesterol.
I think that we had less problems because I was in my early 20's and I was very motivated! We needed little if any lub because my body was producing a lot. I was extremely aroused and my body had all the hormones it needed.
We did not succeed the first time, tho we got close the third. I can't remember all the details but the first time he was able to get in, it was so tight that he really could not move. It felt as if my urethra was being stretched. If he moved it got worse. So we just maintained that for the next 3 times...maybe.
Now, I'm 22 years older and my body has changed. My vaginal wall (the skin) is probably thinner and I probably produce less lubricant. Hormones and the degree of excitement can influence how elastic the vagina is at that time. I think we would have a more difficult time if we were having sex for the first time. I think you said you are not circumcised, and neither is my husband. So, as much as the glans is more moist and I thought that may have helped us, you have the same situation. So, that is not a problem.
I'd just keep the faith and make sure you are always dealing with a professional who understand this kind of situation. Not all OB/GYN docs are that educated in sexual difficulties. They know the reproductive organs and how to keep them healthy.
I think you're doing everything you can, and the glass dildo's should also help. And, maybe a very low dose of testosterone-or just keep that in mind.
But don't give up.