If you read the law, it requires a majority of electors APPOINTED.
Since there are 538 appointed electors, the number is 270. If 39 electors did not vote(as would be the case here effectively), the number remains 270. That number is immutable in the 2016 election.
Nope - you are missing a very critical point.
The electors are appointed by the states. The scenario being discussed involves a state failing to appoint electors.