Impeachment has no chance whatsoever. Its not even constitutional. The Senate has no authority to hold court over a private citizen. Not to mention political suicide for Senators
What are you talking about? Do you think they're going to arrest him and throw him in jail if the Senate votes for impeachment?
If he was still in office, he'd be removed from office. Since he's not in office, if they impeach they will move to a vote to bar him from ever holding office again. 14th amendment I think. There is precedent for exec branch leaders being previously impeached after their terms end, and there is nothing in the constitution specifically requiring the person to still be in office.
We shouldn't view this as McConnell suddenly having a conscience or something. It's purely a political calculation that he can leverage this action to permanently remove Trump from the party.