Welcome to YT & congrats on Sophie!
Travel: I have boarded Huey at the vet twice since we got him (he is now 4 1/2) but DH & I have decided that unless it is a dire emergency, we will always travel to dog friendly places from now on & take him with us. As for ruining potty training, no clue. We haven't had the best of luck in that area-it is hit or miss.
Food: you are lucky to have a good eater. Yorkies have a tendancy to be picky eaters. There are many threads here debating the brand of food that is best, but I will weigh in on amount. I feed Huey 1 tbsp per lb of body weight a day, split into 2 meals. He is 8 lbs & gets a little less than 1/4 cup (4 tbsp) twice a day of Blue Buffalo Freedom. This gets supplemented with training treats, carrots, frozen green beens and the occasional piece of cheese when I can't resist the face any longer.
Looking forward to pics!