Near...back when I was a low desire wife, if my husband had made it clear to me that he was truly unhappy and was considering divorce, and then he offered a book for me to at least TRY reading for the sake of our marriage...I would have actually been happy that he was being pro-active rather than fuming, pouting, or generally being grumpy about it.
Also, you basically are using your wife's previous statement that she'd never do counseling again as an excuse for you to not be proactive about that and basically demand it. You don't want to step into the shoes of being the bigger person and putting your 100% effort into making changes that may save your marriage. Trust me, I am not getting down on you as I made the exact same mistake. I am divorced now and I'm pretty sure my marriage could have been saved if we had both not been too stubborn to be the bigger person.
If my ex-h had come to me with sincerity in his eyes and voice, and simply said "I love you but I cannot stay in a sexless marriage, I do not blame it all on you and I want to do whatever I can to make us happy again", and especially if he had done some research...well, my heart would have filled up with love for him had he done that. But instead, he did like you are doing: he assumed I duped him and that I was on my way out the door anyway, so why should he bother to be a better person for me?
Also...the child having cancer and chemo...this is a really really huge issue for you both, and I feel horrible for you...it really has to have a huge impact on every part of your lives. Some women (and some men too) just completely withdraw their sexual energy during trauma and crisis, and then sometimes, you don't use it and then you lose it. I feel this may be true for your wife.
Please just try some of these suggestions...but first you are going to have to committ to doing things a better way, and keep doing them, even if your ideas get shot down.