For the most part I agree with your analysis of the situation. It will be nearly impossible to get a conviction in the Senate short of Trump being found with a live, naked Russian boy in his bed. He has already been caught being unfaithful to his wife, shown to be a felon and admitted to grabbing women he hardly knew "by the pussy." That's barely raised an eyebrow among Republican Senators. Warren hatch was amazed at "how good Trump is" considering he came from New York. I don't even think that the cascade of money laundering and tax evasion charges about to descend on Trump will be enough, nor will even his having been found to act in direct violation of the Constitution and his Oath in a Court of Law. (see the emolument cases going forward at this time.) There is something, however, that in my opinion might possibly be enough to get a two-thirds vote, short of the romp with the Russian boy I mentioned earlier, and that would be irrefutable proof of his campaign having paid for some of the Russian Hacking and/or actively having coordinated the Hacking with the campaign. But even then, I'm not sure.
Of course, once Trump's toady pick for the Supreme Court, the oleaginous* Kavanaugh, is safely on the bench, the Republicans will breathe easier no matter what transpires with the pugnacious, veracity-challenged Mr. Trump. But wouldn't it make sense to get this over? Why not Dump Trump, let the obsequious Pence take over; then concentrate on getting Kavanaugh seated? He'd still be the nominee whether Trump is living at 1400 Pennsylvania Ave. or in Morgantown -- ping pong, bumper pool, but no golf, classes in plumbing available . Or do it in reverse order, but do it quickly. If instead of looking like fools and furnishing material for 2018 Democrat political ads, the Republican Senators started acting like responsible adults and concentrated on dumping Trump and putting Kavanaugh on the Bench, I think they might actually be able to redeem themselves (some) in the eyes of the American Voter, and possibly shorten the party's period of ignominy that's bound to follow.
With the seating of two young, radical-right Justices, McConnell & Co.'s work will be over. There will be no need to prolong the ridiculousness. The longer they pretend their President has done nothing wrong and praise him as being at least as good as can be expected coming from New York, the longer they look like fools. The sooner they dump trump and wash their hands, the sooner they can start to regain credibility. It won't take long, we voters have short memories.
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* a delightfully apropos descriptor borrowed from George Will.