There are so many variables about how long recovery takes, but I can comment on the growth aspect. My youngest was DX at 18 months (after dropping off the charts between 12-18 months. When she hit 3 years she finally started looking like a typically sized kid - "normal", just a little smaller. I'd say it took about 9-12 months to go from the little twig limbs to what you'd expect. She started wearing 12 month clothes at 12 months and didn't jump to the any other size until she was well past 2. Now that capris are in style she's back to a lot of her 18 month pants - perfect on the waist, just below the knees for playing. Fierce, but mighty!
We totally went through that stage that nobody believed she should be walking and talking because she was so small. Honestly, her vocabulary was light years ahead of most kids at that age so that totally threw strangers - she was infant size, but carried on these amazing conversations.