A friend of mine actually discovered his latent schizophrenia through Marijuana usage. So yeah, not as safe as people want to believe. I honestly think that there is less mental health risk in taking MDMA, Speed or Alcohol compared to THC.
Glad to hear that someone else finds this direction interesting. I actually built something in that direction half a year ago: https://owleo.com
But I mostly abandoned it for now, as expii.com seems to be pretty close to what I wanted to have. Also since I finished my studies, my learning changed to be more explorative and need-driven, which didn't fit well into the thinking behind Owleo.
The better advice is imo to keep your browser up-to-date. JS exploits have been come increasingly rare these days, mostly due to Chrome's excellent example of patching quickly and paying good money for exploits (e.g. Pwn2Own). JS 0days are imo far too valuable now to waste them on normal users. So no, disabling JS wouldn't make much sense, if your have an evergreen browser.
Disable Flash & Java and try to minimize downloads is the security advice I give nowadays. Also don't install anything unless you absolutely have to (there are plenty of good in-browser options for programs we used to install, e.g. for file conversion).