Everything about Scott's cognitive state (I.E. seizure damage, damage from drugs, reactions to behavioral medicine)is all speculation at this point. But whatever condition he's in, I don't imagine its something that can be treated that he's ignoring. I think this is just the way he is now, and we have to accept that.
However, one thing we do know is that he drinks. A lot. It's clear that when he's sober he's a lot clearer speaking and thinking. So the number one thing Scott needs to do for his health and performance level is to quit drinking entirely. He has to be 100% sober.
Secondly, he needs to take a lot better care of his voice. A vocal coach, daily exercises, and a use of a vapor inhaler prior to every show followed by full vocal rest afterward could go a long way for his voice. We're never going to see him back at his peak, but I think returning to his vocal shape from 2009 is an attainable goal.
Finally, I think he does needs an extended break from the touring grind. He's been touring almost non-stop since 2012.
But let's be realistic. Scott was fired from STP because he refused to do these things. He drank like a fish, gave no consideration to his voice or performances, and when the rest of the band told him to take a break to get in better shape he turned around and did the Purple to the Core tour instead.
That's the frustrating thing about Scott, he can be a lot better performer these days if he just tries. But I think its clear from his behavior of late that he really just doesn't give a shit. He wants the paycheck and that's it.