My recollections are:
Recusal - it is a “personal ethics” choice. No one can cause another to recuse. Ethics panels are an after-the-fact remedy.
Attending Senators: The Senate will suspend all work until the Impeachment is decided. Senators will have no excuse not to attend. There is uncertainty about truant members. At this time, I believe that all Senators will attend. Sanders and Warren may travel extensively on weekends (schedule?) but will be in attendance. Booker, of course, will attend.
You see, they need to have the vote as close as possible and strictly on partisan lines because a trouncing in the Senate destroys any credibility gained in the House. If the vote spread is greater than 10 (10%), they will bleed more moderate votes.
My Dem wife (actually a moderate-right Dem) confessed the other day that she can’t stand Trump’s personality but doesn’t fault him for the accomplishments (she’s in banking).
“I won’t vote for him but the alternative ‘sucks eggs in the rooster-coop’.” She ain’t voting for POTUS at all.