Re: Jace's tactical vomiting:
I actually have a medical condition called "gastric reflux" with remarkably similar symptoms. It comes on after eating, and strong smells set it off too (But I'm pretty sure that bit is just me). It comes on pretty fast, which is consistent with how Jace is behaving. I'm on medication to control it, which works fine, but it can still be set off by eating too much junk in a short period of time.
Given Jace's fondness for eating nothing but junk throughout his stream, it's possible he has a similar condition that he could get along just fine with if he would, yknow, stop eating when he feels ill.
Stressful situations bring it on strong too. For me, that means exams. For Jace, that means people illegally disrespecting wolves or being shown a picture of an Islamist terrorist Al-Gamerfood duck.