“If he’s impeached and convicted they can then vote to ban him from public office.”
That sounds to me like a Bill of Attainder. I don’t think it would be Constitutional (if that matters anymore).
Conviction immediately removes the defendant from office. Following conviction, the Senate may vote to further punish the individual by barring him or her from holding future federal office, elected or appointed. As the threshold for disqualification is not explicitly mentioned in the Constitution, the Senate has taken the position that disqualification votes only require a simple majority rather than a two-thirds supermajority. The Senate has used disqualification sparingly, as only three individuals have been disqualified from holding future office.
Why would he even want to hold office again. It would be another four years of hell for him and his family. He should go out scorched earth. Release everything, leave a gone fishing note with a big FU, use his remaining “sick days” and disappear.