Much of that slang is just old and none is made up by him. The consistency of application is something that should be noted though.
I know "gag a maggot" is at least +30 years old from when I was a kid. It could be older. I also grew up in NC, so the slang could have even been regional.
I am in my 40's, so it's around the same era. All I am saying is that I have heard all of that slang before and it isn't made up. (I even occasionally use "gag a maggot", actually.)