It's not happening, but under the Constitution, I believe it's one vote per state delegation and the Republicans hold more of them. Trump would win in that scenario.
Not necessarily.
If those EVs went for Johnson, the House might vote for Trump.
But what if Gary Johnson decides to instruct his electors to vote for Ted Cruz? Or Rand Paul? Or Paul Ryan (much less likely).
I would estimate that at least half of the GOP House Members are markedly unhappy with Trump's nomination, and are not sure whether or not they'd rather he win or lose. If Trump is the projected EV winner on Election Night, I won't believe he'll be the President-Elect until the Electoral College meets and the votes are counted.