Hey Blue!
I haven't finished distracting yet, but I'm very close to my goal of 7cm already. I've noticed that I've definitely lost the flab in my arms and have gained muscle definition from pushing the wheelchair for the past two months. Also, shoulders and chest have gotten stronger from lifting myself to a standing position with crutches, as well as from lifting myself up stairs.
Peculiarly, I've also noticed that some of my t-shirts are shorter. I think this is because femur lengthening somehow changes the biomechanics and you're forced to stand in different way, which affects your posture. I used to slouch a lot before my surgery. (Or maybe it's because I have more self confidence now and I stand taller).
Although you're not doing resistance training in your upper body at the gym, the fact is you're still going to the gym almost everyday. It's logical to assume that your body as a whole is adapting in some way. Also, hefting yourself out of your seat or into your car everyday without putting stress on your legs takes more upper body strength than you realize.
Since returning home, my belly has more fat. Mainly because family is pampering me so I'm eating too well and sleeping too much. When I put all these factors together I do notice a difference in my pre-op size. T-shirts that used to fit "just right" are now "a little too snug". I used to be a chubby guy when I was younger, so I know what you mean about having a big face. If you're worried about obesity try going on a very low-carb diet for about two weeks and see how it goes.
I think a little bit of weight gain is normal, though. You are, after all, growing. I think it would be weird if you didn't gain weight since you are increasing in mass. Just to give you an idea, I'm roughly 5% taller now, and 7% heavier. If my math is correct, you are 6.2% taller than before and you are saying you're 5.9% heavier now. I can't say for certain that there's any direct relationship between height gained and weight increase, but it's pretty logical to see that there should be some natural correlation.