You could try feeding him black jelly beans before the next show
. No just kidding... his mouth pigment is what it is, nothing you can change .
As far as his chest, Time will take care of that, he is only 12 months old right? he has alot of filling out to do over the next year or two. Feed and exercise him right and he will be fine.
I think judges have to say something to validate their placements. and I would not get too upset with an SG rating it means very good and is the best rating he can get as a young dog.
Also, and this is just my opinion, but I will not show again until my boy has gotten older, bigger, and filled out more. I showed him as a 6 mth. old(6 mth and 2wks old) and the youngest in his class and he did not do as well as the larger more mature looking pups.
I will try to pick a show where he will be at the older end of the class. Congrats and good luck at the next show.