He would have certainly lived if killcop had got off his neck. Even if the OD theory were true you can't give Narcan to someone while you are choking them to death.
He wasn't being choked to death.
You don't administer Narcan (naloxone) to someone unless you know they are overdosing on an opioid.
What Narcan does is offset the effect of narcotics. And narcotic junkies don't like that because they know they will go into withdrawal, and get very sick.
Usually when a person ODs on a narcotic they just go unconscious, they don't go into some bizarre psychotic episode like Floyd did.
Because of the toxicology report, in retrospect, we now know that Floyd wasn't merely taking a narcotic. He was also on methamphetamine. He took fentanyl and methamphetamine. AKA a goofball, which is similar to a speedball, the shit that killed John Belushi, only much deadlier by an order of magnitude.
Floyd ate what appeared to be Percocet tablets. But they were counterfeit. The active ingredients of Percocet are oxycodone and Acetaminophen. What he took was fentanyl and methamphetamine.
The cops asked him several times but he wouldn't tell the cops what he took. And neither did his so-called "friends" that were in the vehicle with him.
For all we know, one of them gave him the counterfeit drugs to murder him. After all, a guy like that who would rob a pregnant woman no doubt tends to make a lot of enemies who would want him dead.