Masuli:
I would say he should gain slowly or faster but take little breaks so that his body can get accustomed to carrying the weight on the longer run.

Weight training would be good if trying to keep mobile while gaining weight.

Also suggesting adding vitamin D & Calcium or checking levels on blood for bone strength, this is important when carrying extra weight.

Munchies:
Collagen is good too. Keeps the skin supple as you grow and promotes joint health.

Dolkite:
I had a complete stranger prod my belly at the grocery store once. I wasn't even wearing anything tight or too small as I've been known to do in the past. I'm not sure if she was trying to humiliate me or poke gentle fun. Either way, I enjoyed it as a sign that I had gotten fat enough where someone felt it was appropriate.