I think this election may be as much about turnout, Needs - as it is swaying independents. The independents Trump already grabbed have plenty of reason to stick with him - as the reasons they DID have come to fruition. Grabbing more independents - gravy - and would be done through the debate season, I'd think.
The talk is how Biden is getting turnout that Hilary didnt - and also getting a higher male vote (see Michigan) - which is promising for your side.
1. Polling does not show independents sticking with Trump. In head to heads against Biden (or Sanders)
https://poll.qu.edu/national/release-detail?ReleaseID=3657 or through impeachment when a majority of independents wanted him gone.
2. I don't know what you think has come to fruition under Trump that independents approve of. I know you won't answer that, as you consistently dodge the question on what Trump has accomplished. But his signature accomplishment, the Trump Tax Cuts, are enormously unpopular. And had he accomplished what he wanted on health care we wouldn't be having this conversation because he likely would have been impeached. Which is why Republicans are trying to accomplish this via the courts, and making sure those decisions come down after the election.
3. Trump camp knows their candidate will look weak in debates. He did against Clinton, and his cognitive skills look to be in decline since. Which is why, as I said, they have laid the groundwork to skip them. My opinion, had Warren won, he doesn't debate her. Against Biden he may, but its not 100%. In any case, the contention that he gains followers during the debates is contrary to the historical record and...debatable.
4. Yes, turnout helps Biden as what will be driving the higher turnout (as with midterm elections in 2018) will be the anti-Trump vote. And yes obviously, Biden is expected to do better with working class voters than Clinton did. This is why Trump fears that match-up the most. And was making impeachable maneuvers to weaken him that a Republican Congress, to their shame, is doing their best to continue.