So what your saying is:
That if a bullet and even a casing match the Glock, and George's prints are on it, that still can't prove George used it that night. I would say it would be very strong circumstantial evidence.
Then add in CN's testimony about buying a Glock and being a Glock man. Then there is Jake's gun list on his phone listing the guns for each family member. If George is listed as owning a Glock that is strong circumstantial evidence, and so is CN's testimony - if he were to testify.
If Jake's prints are on the gun then maybe Nash will put it the way you describe, that Jake "borrowed" the Glock and used it himself. I don't think the Jury will buy it.
I think its obvious this was a 2 or 3 person crime, too much just for Jake to pull off alone.
Plus, there are 2 different sized shoe prints, It is not reasonable that Jake anticipated blood on the floor and brought a pair that fit George to leave "George's shoe Prints."