We need a robust addiction support network to go along with that, but, yes: illegalizing drugs causes more problems than it solves. Legally regulated and sold drugs ensure quality and provide confidence that what the consumer is getting (and ingesting) is what they think it is.
Street variant. The dosage needed to get high or overdose is so small that its much easier to smuggle in compared to other drugs
AFAIK the medically its only really used for anesthesia which is usually used under controlled conditions and makes responding to very easy, especially when there's OTC drugs that reverse opioid overdoses, though fentanyl can take multiple dosages to reverse