Sure.
Sure.
There's certainly no standard, and it's not necessarily "as far as you can reach" either.
If you're doing an actual snatch, your grip width will depend on your arm lengths and also require some experimentation to find a good balance between your individual ability to stabilize the bar overhead and the vertical distance you'll have to pull it. To understand this, imagine doing a snatch with a clean grip - it might be a lot easier to stabilize overhead (essentially the lockout position of a press), but you'll have to pull it really damn far to be able to get under it in one motion. Conversely, you could grip it out by the collars and not have to pull the bar as high to be able to get under it with locked out elbows - but it can be very hard to stabilize a heavy weight with that grip width due to the moment arms on the shoulders.
Now, If you're just doing snatch-grip deadlifts, most of that stuff doesn't really matter. If you want to make it harder, go wider since you'll be "shortening your arms" more. You can see where I grip mine on an Ohio Power bar here: https://www.youtube.com/watch?v=czOGduPxdSc maybe a hand width (or a bit less) in from the collars, or a bit wider than you're describing. Not a huge deal either way, as long as you're consistent.
The grip in the snatch places the barbell in your hip crease when you stand erect. That is the width you would assume for the sgdl, as well.
Edit: Or whatever Austin says
Right on. Fucking awesome pulls too. I watched the video, that was impressive.
EDIT: Thanks Cody, MG.
Pretty much agree with you though, and that's certainly where I start most people (especially when teaching the snatch). But for people only doing SGDLs where there's no concern about a second pull or overhead catch, it becomes less important and you can easily go wider or narrower to play with the mechanics/difficulty of the lift. I've tried doing SGDLs with a grip all the way out at the collars and man... it gets damn hard to break that thing off the floor.