If you are facing these issues on a personal basis, then I suggest consulting with actual oncologists and reading textbooks on the subject. Also, seek psychological counseling. When the fate of a loved one, or yourself if you mean a really personal basis, hangs by a thread for an extended period of time, it will eat you alive every waking moment without help.
Will do you better than polling the public.
My two cents, since you asked for them:
1. Medicine is made to cure or treat illness. The pharmaceutical industry relies on that necessity to overcharge for drugs, but medicine won't make it to market, or won't be recommended by anyone's doctor, if it doesn't have at least some credible proof of efficacy. Health care is a business that will always be in demand, so there's no reason to create false business by distributing weaker drugs or making up diseases just so you can sell sugar pills for it. Even if you did, another company would just release a legitimate one and drum you out of business.
2. Like all charities, it depends who you're dealing with. When at all possible, it's advisable to donate money directly to the source you want to receive the funding, or as close as you can get.
3. Since cancer comes in so many flavors, I doubt there's any one overarching "cure for cancer." I don't see any reason to cover up a cure for cancer -- there is a lot more to be gained, even money for the heartless businesses, by releasing such a thing. I'm very curious what reasoning anyone's giving to that theory. However, while
curing cancer is out of grasp,
treating cancer has improved remarkably. Again, there's a lot of variety so it depends on the details of each situation, but it's not generally a big scary death sentence like it used to be.
My father is a family physician with whom I have worked very closely, so I feel confident in saying that there are flaws to the system, mostly in costs and anything to do with for-profit health insurance, but the products of modern medicine are designed to heal you.