Regarding the Chazon Ish neurosurgery story, as has been discussed here previously, there is no source other than books quoting other books with no name of a doctor or hospital or patient so that it can be verified.
In additon, if it was true about the Chazon Ish, then gedolim of today should be able to do the same thing. But yet, the Steipler and Reb Moshe and today’s gedolim all go to hospitals and submit to the doctors treatments. They do not stay home and treat themselves with their advanced knowledge of medicine. None have claimed any knowledge of curing cancer.
Finally, there is a tshuva in Reb Elyashiv’s sefer regaring whether one can lie and make up stories of gedolim to inspire talmidim. That pretty much says it all.
(Reb Elyashiv strongly discouraged it, in response.)