Wow, just reading your story it is very obvious how much you love & miss the intimacy you & your husband shared. I am truly sorry for that loss & it must be horribly difficult for you...... I assume you have had heart to heart talks with hubby about the differences in your libido's & the effect his lack of interest is having on you?
Sex for me has always included a huge mental aspect, < I just assume that to be true for most of us. After all, our greatest sex organ is our mind.
It would also seem to me, if he clearly understands your frustrations, he would want to continue to please you intimately & even though he may not have the sexual release it seems he would still be thrilled by the touch of your hands & lips on other erogenous zones on his body. I truly hope you can talk things over with him to your mutual satisfactions.
I worked with a fellow one time who was in his late 70's, that had a similar operation/situation, he actually had an implant installed that he could use to pump his penis up to an erect state & still have intercourse with his wife even though he himself would get no release.
Good luck Justmenow.... & please let us know how things go..
~Bdm3~