The implication of working coronavirus vaccine by end of October was that it would be available for use (you can find quotes from the Trump administration saying they were working on distribution of hundreds of millions of doses by the end of the month), not that there would be a preliminary report from a still ongoing trial indicating that the vaccine works.

The Steele dossier includes information from Russian sources. It was not "paid for" by Russia.

No one has argued that Hunter Biden was not being paid because he was a Biden. The question was whether it led to improper behavior on the part of Joe Biden. That email proves nothing. It's entirely plausible that Hunter Biden got this guy an invite to some social function where shook hands with the Vice President. This is also entirely ignoring the fact that the firing of the prosecutor wasn't some sort of one off idea that Biden came up with on his own. There are independent speeches by all sorts of people from 6 years ago that complain about the corruption of the prosecutor in question, which makes this whole point moot. The prosecutor was fired for not investigating the company that hired Hunter Biden.

Like most liars, Trump isn't inventing everything out of thin air, but he misrepresents so often and so much that you can't draw any useful conclusions from anything he says.