First of all,
hydrophilic attack , I'd like to say thank you for putting together a pretty well thought out OP, presenting a pretty good framework for discussing this.
Of those options, 3 seems like the most plausible solution, though I wouldn't be against a Bernie nomination either.
Towards options 4 and 5, I'd like to say that the American public is generally not good at making collective decisions, i.e. weighing outcomes to find the greater good. But I wish we were. We were all taught that a vote belongs to each us individually, each vote should reflect our own personal wants and opinions, and the chips fall where they may once they're counted up.
But a democracy was intended to have dialogue, (real) debate and consensus-building, especially within our own sphere of thinking. That is even more true in a very polarized two-party system. We can't escape that "Democrats," as a tent, are going to have to weigh a lot of positives and negatives. We've been in ugly political situations with unsavory politicians for a long time now. It's all we have to work with.
I do get the sense, like many others, that our political process is horrible and sliding backwards into the abyss. But is the solution to just disengage from it entirely? Don't vote and just watch everything burn? That wont fix
anything. Do we just give up because the choices are hard? We really shouldn't. At the end of the day, millions of people suffer or prosper based on our individual ability to find the time and the will at a ballot box. That's what votes should be based on - the outcomes we want the vast collectives of people in this country to have, not who gets to sit in the oval office and what cult of personality they bring. The best outcome for us right now might be for a D president to rubberstamp a D House and D Senate to try and stop the bleeding.