Matt Burnett did have a tweet that stated if Steven were to poof, he would die. It was taken down for whatever reason--inaccurate information, spoilers?
I believe that if Steven were to poof, he would die.
Gems are projections of their gems, gems are gems. When they poof, they return to their gem to heal. Steven isn't a projection, he's flesh; he doesn't get energy from his gem. The only thing he got from his gem was half of himself (and powers). "DNA".
"You can't cram a body into a gem." is basically my argument.
I agree. Steven's human half is what makes him so vulnerable and his powers so fickle. The gem powers were made for gems, and having a hybrid makes them... fickle at best, unpredictable at worst. Despite being half gem, Steven is still a human, and he would not regenerate if he were to "poof". Though I think poofing Steven is impossible, so if you squeezed him to death you'd likely get a pool of red instead of a cloud of grey.
"We all want progress, but if you're on the wrong road, progress means doing an about-turn and walking back to the right road; in that case, the man who turns back soonest is the most progressive." ~CS Lewis