I guess that a range of 6.5-7.5 would be ok for humans.
Well it depends on where you are talking about in the body but as a general rule the body keep blood levels between 7.35 and 7.45 bar in abnormality and crisis when it may occur outside of those levels although the body will be compensating to bring it back to that level.
Certain cannabinoids can potentially aggravate cancer, but most studies seem to suggest an overall devastatingly positive effect.
But shush! its taboo, it's ILLEGAL!!! you'll never get a research grant for ILLEGAL NARCOTICS!
That last statement is simply not true there is a wealth of research that has been funded into the links and the all broadly find the same thing:
Smoking cannabis increases the risk of cancer.
There is mixed evidence of the effect of THC (and other cannabinoids) on cancer cells with evidence showing antineoplastic action but also there is good evidence that they also impair the immune response to cancer cells.
That THC (etc) may be a useful adjunct to some of the complications that cancer suffers get eg decreased diet, neuropathic pain, etc.
So let's say take someone who smokes cannabis:
They will directly and profoundly increase their risk of developing lung cancer.
The cannabinoids in the cannabis will increase the LAK lysis rate on found cancer cells.
The notion that smoking cannabis protects from cancer is then plainly wrong. The cannabinoids will profoundly increase your risk to the very thing you are trying to stop.
Does that mean cannabinoids have no place in oncology. Then of course not there is abundance of evidence to demonstrate their actions will be useful and should be fully explored. There are a multitude of funded studies into this strongly disapproving your last point.
tl:dr - Smoking cancer increase your risk of cancer, some stuff in cannabis has benefits for people who already have cancer, stoners will mix the two up and justify their smoking for its alleged medicinal properties.