This entire discussion is about semantics, so I see no issue with getting fiddly with it. As for authoritarianism being illiberal, I don't see how that is tautological. Authoritarianism is when the government or ruler has absolute control and has no obligation to accept input from the populace over which they rule. This violates the consent aspect of liberalism. These are commonly accepted definitions, not stuff I just made up. They're mutually exclusive concepts and absolute versions of either cannot coexist.

And yes, I do think there has never been a truly liberal society, just as there has never been a truly communist society or any other -ist or -ism based society. They are concepts we can strive for, but adhering perfectly to the academic definition of any of these concepts is not realistic. I think the USA is fundemantally illiberal in many regards, and we would do well to strive to correct those aspects.

As for the definitions of those specific aspects of liberalism, yes, of course it is those aspects defined under the framework of liberalism. It would just take thousands of words to provide the entire context and it's not super important here. You seem to understand that these words have different definitions in different frameworks, and I'm sure anyone discussing political ideology in this level of depth is also aware of that.

When I'm talking about the extremist sides of the spectrum, far left and far right, I am referring to those who tread into territory where their ideology becomes ostensibly dangerous. The most common version of this is directly supporting things like oppressive authoritarian rulers and population cleansing, There are absolutely people on both the left and the right who would see those as acceptable means to their end of implementing their preferred ideology. Right wingers who want to ethnically cleanse populations they see as problematic or inferior are no better than the far leftists who want to guillotine whoever they decide is the bougouise. This is the crazy land I'm talking about. Not being in crazy land means trying your best to not support awful shit, making sure you are picking the least bad feasible options in your current situation, and revising your positions and who you support when evidence indicates that the bad outweighs the good.

And yes, I actually do have a lot of issues with the French and American revolutions, and I do not think Churchill was a particularly good guy. I don't think they are the same as the Russian and Chinese revolutions. They all resulted in regimes of varying levels of "bad", but the Chinese and Russian versions resulted in higher death tolls and much more unhealthy systems coming out the other side (in my subjective opinion).

I think to cover the rest of your points, there are degrees here and the real world doesn't function in absolutes as I mentioned in the second paragraph. I don't have time to respond to every comparison you mentioned, but Washington vs Lenin for example: Washington did not have secret police killing dissidents by the thousands. Lenin did. Washington did not implement policy that resulted in mass famines resulting in the deaths of millions, Lenin did. Washington did support slavery and ethnic cleansing of Native American populations, and it irritates me greatly that this gets glossed over. Lenin did not. Which one of those guys is worse depends on your subjective values, but for me, I'd say Lenin is the worse guy.

I'm tired and it's almost 3am so hopefully all that makes sense.