Lol, my mind went straight to Mitt Romney with that description.
LOL... Remember how his face looked like it actually ached from that fake grin? People don't trust that.
and all the reasons you listed above are the reasons he can't win
Look at some of the most respected leaders - the ones with "gravitas" - think of Mandela, Jeb, Hilary, Reagan, Cheney - They didn't put on a fake smile. They had too much confidence to do that. (Even if you hate some of them, you had to admit, they didn't use the fake smile).
In 2016, imagine Jeb and Rubio in a debate. Rubio either looked flustered, or fake smile. Jeb has that same "I got this, everyone chill out" look to him. Cruz has that too.