1. I'd say GUS-tav
2. That is pretty ethnic, but I've heard it before on people from several different generations so it doesn't come across to me as being
ridiculously ethnic or anything. It's definitely useable, IMO.
3. I like it. I go back and forth a bit with how I pronounce it, but all in all I think it's a good name.
4. Another 'gus' name that comes to mind is
Fergus.
I have a new little relative named
Angus Leo and I think it's an awesome name. So... someone likes
Angus!