That's pretty much what happens when you get a stemcell transplant. Luckily there is steady improvement in the survival rate. This is a very old therapy by now of course. But let's hope the various form of immuno therapy take the same trajectory, getting a little better every year.
Taking one gram every 5-6 hours for a maximum of 4 gram/day IS entirely reasonable.
I don't know how you jumped from "it's dangerous to take in to high amounts, even 4 times the recommended dose is dangerous" to "the recommened dose is dangerous".
When taken correctly it is very safe and had fewer side effects then NSAIDs like ibuprofen.