The thing I would note in regards to point 3 is that this factor has an n>3. The trend whereby polls overstate liberal/left-wing performance is traditionally called the "Shy Tory Effect", getting its name from when it was first seen in Britain in the 1990s. It also happened recently in Brazil, with polls greatly underestimating the strength of Bolsonaro and his allies.
Granted, nobody knows what exactly causes the Shy Tory Effect, and so a reversal is in principle possible based on obscure factors. But I think the body of evidence supporting a polling error that benefits the GOP is stronger than you realize. There's definitely also been neutral elections, but I don't know that it is historically supportable to say that a polling error benefiting Democrats is as likely as one benefiting Republicans.
What has happened in other countries is totally irrelevant to the US. It doesn't matter that sometimes the right benefits from polling error abroad. We also know that the left sometimes benefits as well - this happened in Chile last year, so what?
In the end, empirical evidence from the US shows that polling error isn't systematically associated with the right or left over the past 40-50 years. Sometimes Democrats are underestimated, sometimes Republicans. We do know that in some states, Democrats are almost always underestimated and this is true for the GOP as well but, nationally, we really are relying on a few elections that happened recently.
To be clear, I think Democrats will be crushed on Tuesday and that GOP will benefit from polling error but that's more about non-response bias related to "low social trust" voters and not about "shy Tory" - latter is very different phenomenon. A certain type of working class voter won't respond to surveys - not the same thing as someone lying about their preference.
You do make a valid point that I should not be associating this with what happened to the Tories in 1992 since GOP voters today and the UK Conservative base 30 years ago are very different groups. With that in mind, I think it is somewhat misleading to look at "empirical data...over the past 40-50 years". The GOP base has changed quite a bit over that timeframe, and the most recent shift related to Trump's rise is likely related to the emergence of this polling error.
