1) On the "conservatism" issue, I think it'll get worse for them before it gets better. But it still seems to me that a much larger, but currently less vocal, contingent of people in the conservative ranks of the country will just let the Trump wave peter out. And I think it will. Maybe not immediately, though. One way Democrats will quite possibly mess it up is by charging too hard to the left. That could make them lose the center.
2) Fully agree on McConnell. He's the definition of "Party before Country." But there are Democrats like that, too. Lots of them. Nancy Pelosi and Diane Feinstein most certainly.
3) Right with you on Trump, who I didn't vote for either time (I've almost always voted Dem in my presidential voting life). Trump was about Trump more than anything else. His personal behavior and financial brinksmanship shows you that. In a real corporate CEO position, he'd not last a year. Maybe not even a month. Too reckless.
4) I don't know that I agree that the Republican radicals are "running the show" for them right now. But they clearly have enough pull to move the party toward them. That doesn't end because Biden started a week ago. That will take 2-4 years to peter out. If they do not make big gains in the mid-terms, that group starts to lose power more quickly.
5) I don't know that you're right about zero Republicans working with Biden. Unlike Pelosi (to an extent) or The Squad (for sure), Biden has a long career of actually doing that - working with Republicans. He actually seems to be reasonably respected by them. You're probably right that they won't just jump in with two feet. He didn't help himself by big showy acts like immediately canceling the Keystone Pipeline without further review, either. Pipelines are significantly safer than doing what happens today - taking that material by truck and train. The debate is over on that issue - there are real stats. He was placating his left wing by doing that, of course because he has the same problem the Republican leadership has. If his radicals gain too much pull, his party will falter.
6) Right with you on the criticism of many state legislator Republicans. I grew up near but not exactly with the worst of the far right Oregon ones. Those people are just too sheltered from the world and don't know which end is up. They believe they American Exceptionalism hype.
7) I wanted to go through Sanders' platform again and post something there, but it just got too busy to get my thoughts together. What I remember that last time I looked, though, was that I didn't at all feel his proposals looked like FDR. It had way too many aspects of government control (not just financing) of the projects he wanted to launch. All sense of cost control and investment discipline would go out the window. I just feel it's unworkable. So is the Green New Deal, although I would support aspects of it.
