Re: glass backsplash
I think I would be inclined to rest it fully on the existing counter backsplash - no channel, then either use mirror clips along the top edge or have the glass drilled and run attachment screws through and into framing members. Once the glass is installed run a small bead of caulk along where it sits on the counter to seal it tightly so that no dirt or debris can get under or behind the glass. The other thing is I'd recommend that safety glass be used. Safety glass will pebblize if broken, it won't shard as normal glass will, and if you go the route of through fasteners, then the holes need to be drilled before the glass is tempered and treated.
The reason I wouldn't suggest using J-channel as previously mentioned is that you'll see it through the glass and it won't be very attractive. Using a wood frame isn't a bad idea, however I think you'd still have problems with grime build-up if it's not sealed with caulk. Also, wood in and around a sink isn't the best idea as it will be prone to water stain and damage for constant moisture.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!