My argument may be 'all over the place', but you seemed to have followed it pretty well.
"How exactly would legalization hurt Mexico? Look at Portugal to see how we should all move towards dealing with drugs and addiction as a health problem instead of a criminal problem."
Portugal didn't have cartels running entire sections of the country. Drugs may be part of the problem with Mexico, but the cartels are too powerful and legalizing them will not solve the corruption problem..and the violence will continue.
"The violence in the 1930s WAS caused by the prohibition, sure it had lasting effects but ending prohibition was still the right move."
It was. But we had a corruption problem as well. Criminals don't just go away overnight. There are plenty of other ways to make money, once you have money, power, and influence. Legalizing drugs will not solve the corruption problem in Mexico.
"Can you cite the rise of black market marijuana in California? The market is doing well and bringing in good tax revenue in every state I've read about."
A simple google search:
https://reason.com/video/californias-new-recreational-mariju...
https://www.latimes.com/politics/la-pol-ca-gavin-newsom-crac...
https://www.forbes.com/sites/kevinmurphy/2019/04/04/cannabis...
"As for the opioid crisis, the issue wasn't that people one day decided they wanted to get hooked on them. The issue was they had pain or were recovering from a surgery and were being prescribed highly addictive medication that was being pushed by pharmaceutical companies without proper warning or care. Marijuana could have been given in these cases and it without the same problems of addiction."
Who decides to get hooked on anything? Some people get addicted to things faster than others. No matter how many warnings you give someone, it will happen...and the company will get sued for millions of dollars.
The cigarette companies are a good example of this. Cigarettes have been know to cause cancer for 50+ years. Yet, we will have people smoking, getting cancer, and suing these companies for millions of dollars.