As I've seen it used, "stonks" connotes that you're suggesting somebody who doesn't really understand anything about the stock market, but thinks that what's good for the stock market must be good for America.
I think it's not meant to suggest a typo, but rather the slurred accent that comes with being overenthusiastic and loud. I'd compare it to using "Murica" instead of "America" to sugges that somebody is being nationalistic -- and I think there's supposed to be a significant (but not perfect) overlap between the two groups.
In some circles, for sure. I've also just seen it used as a goof or an insult. I think it's one of those things that started being used one way but has spiraled off into many different meanings in many different communities.
