... the electors are not Constitutionally bound to cast their vote for their State's choice. The electors are simply given the responsibility of going to Washington to cast their vote.
...
I guess by absolutely wild speculation it is possible although nothing remotely close has happened in the past.
About half the states do have laws binding their electors to vote as the state voted. Interestingly, of those that do not have a legal binding sixteen voted for Donald Trump and their votes amount to a whopping 161. To reverse the election we would have to see a change from the one or two who have very rarely cast faithless votes to about twenty percent of the ones who can. I think the chances are slimmer than slim.
It's my understanding they don't gather to vote in Washington but that they cast their votes from their own state capitals.
As I mentioned we are talking parallel universe events here. Beyond rare.
Yes, there are legal mechanisms that can bind electors to their vote. But they are not Constitutional mandates. They, as you have said, are State and even Political Party mechanisms. (Fines and sanctions) The Constitutionality of these have rarely been challenged. However, in the rare event where an Elector chooses to reverse their vote, I do believe the vote would stand regardless of the fine or sanction.
I know that the Supreme Court has found that such fines and sanctions levied by States are Constitutional but I believe the actual vote "change" would stand.
Yes the votes are cast from their States. Officially counted in Washington.
I thought they were cast at a joint session. They are counted there.