Yours is heart rending story. It occurs to me that picture you paint is not complete. Several questions occur to me: What was your intimate relationship like before this tragic episode? Did you have sex just to please him? Did you indulge in penetrative sex (at present you are willing and he accepts the pleasure of oral sex)? Does he masturbate? Is he incontinent? With some help he can easily find a suitable treatment or method to overcome his ED. These and many other question have to be asked and answered before you can make some progress. I think, like me, most people here would have difficulty to give any advice. I think, if you husband is willing, you could go for couples counselling or sex therapy. There is help out there.
I had the surgery 11 years ago and I know how it seemed to my wife and I that it was end of life as we knew it. Following successful surgery we had to face incontinence and ED. I am still a little leaky and suffer from ED for any practical use. I use a vacuum pump to achieve erection. However, my wife and I decided to try everything to reestablish our successful relationship for over 50 years at the time and now we continue to enjoy our life together.
My wife read your posting and your problem with vaginal dryness.She would like to say something that may help:
A great discovery for us was a particular type of vaginal moisturiser called YES VM. At my age, although I use Wellsprings Serenity Natural Progesterone Cream for Women (wellsprings-health.com), a plant-based hormone replacement cream. For penetrative sex I use amazing lubricating product which can be found by googling yesyesyes.org. I kid you not! It is organic, has no side effects and is better that KY jelly which is rather heavy. I am really allergic and reactive type and if I can tolerate it so will most people. Do have a look.
Before our discovery of this product, because after prostatectomy his penis does not receive natural lubrication he had to use water-based lubricant like KY Jelly for our comfort. We found this quite unsatisfactory because either he ended up using too much (for my comfort) which he found too slippery to achieve an orgasm or too little which helped him but not too comfortable for me. But the introduction of YES VM solved the problem because I could control the amount of lubricant I insert (YES lubricant comes in a one time use tube) and he uses none. And by trial and error we have been able to control the level of lubricant to suit both of us, such that it is comfortable for me but not too slippery for him; win win! Another benefit of using this lubricant is that he really likes the feel of my vagina and he says it feels like old times!
We hope you can find some help.