By the way, before the next question is asked I'll answer it. If a vote is approved, and if the vote ends in a tie... no - VP Vance can't vote to break that tie. Only the sitting senators of that party (in this case the republicans) can vote since it is not an official Senate vote but a private caucus vote.
Who is the President of the US Senate, again? Time to step up? Not yet, but soon?
Vance can't convene the senate, only the majority leader can do that.
By the way, before the next question is asked I'll answer it. If a vote is approved, and if the vote ends in a tie... no - VP Vance can't vote to break that tie. Only the sitting senators of that party (in this case the republicans) can vote since it is not an official Senate vote but a private caucus vote.