Your post just looks like a more complicated 'what is white' post. I will warn you that on reddit we had bad faith posters make these threads daily in order to distract, divide and waste time. If the mods here decide you are doing that you will be banned.

How malleable is whiteness?

All racial and ethnic groups are moldable. That's really what religion, culture, morals and propaganda are all about. They steer the race in certain directions. Why do you think people get so passionate about religion, culture and morality? They intuitively know it steers the breed. Spiritual considerations aside humans aren't much different then crops or domesticated animals. Jews attack and farm whites using this knowledge. They propagandize whites into mixing their genetics into objectively docile, submissive, breeds. Hybrid breeds that do not threaten the ruling class Jews. If you don't know what you are you have no reason to fight for your existence. This has already impacted the white race. Anti natal propaganda has had another major impact. The clear message is either be gay/trans/coomer (hedonic) or be career focused (greed) or don't breed (selfish) or if you're going to breed do it with a non white male because white males = historic and current evil. That's what women and young people are told day in and day out in the west.

Whiteness is even more moldable when outsiders that hate whites (see: Jews) are the ones classifying and defining what whiteness is. Do you see how that works? To people of clear and traceable European lineage being white is not subjective or indiscernible. The definition of 'whiteness' only become an issue when you're an outsider with a grudge or an insider that's been duped into hating yourself and your people.

So who is familiar with any of the significant whiteness studies titles?

Almost everyone on this board.

From my experience with these writings, the authors explain “whiteness” by different parameters than the legal classifications they were subject to.

These are all written by Jews that hate white people and want to genocide us. You shouldn't take anything they say seriously.

The story goes that the Irish, Italians, etc. were seen as “lesser Whites” by the populace in various ways, but how much?

This is a stupid question. These groups weren't seen as lesser whites at all. This is warping of history. Irish were seen as lesser whites because the Oligarchs of England wanted to exploit and genocide the Irish. See: artificial potato famine. This was a divide and conquer tactic use by very very small groups of royalty in European society. Whites, like all races, fight with each other. Africans have tribal warfare. Japanese had different clans and kingdoms. Whites are no different. The European race is divided into different tribes and nations that have moved around and fought with eachother for millennia. The 'lesser' white and 'greater' white thing was just a propaganda tactic to get one group of Europeans to dominate another. War is part of the human condition. War and strife does not erase white identity no matter what a Jewish author or 'historian' says.

Whiteness is said to be defined by what it is not, an opposite to other groups which were racialized by the dominant class

No. 'White' is a very clear collection of unique observable genetics, traits and historical circumstances. Implying that white people only define themselves by subjective choice is a bad faith argument and a subversive idea. This idea is known in american political circles as 'civic nationalism' or a 'choice nation'. It's promoted with marketing hype and bullshit. It's marketed by paid off corrupt cucks like Charlie Kirk and Dan Crenshaw. Before that it was promoted by traitorous asshole like John McCain. These people go to world economic foreign training meetings and study how to lie to the public and convice it to move towards global governance run by a small group of satanic pedophile occultists.

As a result of these rules, they say is that it is still reasonably acceptable to celebrate ethnicities (“Scottish pride”, “Italian pride”, etc.), and that the dissolution of whiteness will even benefit individuals of European descent because it will allow for their individual cultures to be celebrated and for class solidarity to improve.

This is an outdated propaganda model. The newer propaganda is less tolerant of regional European pride. They move the populace towards satanism and sterilization in increments. You're behind about two or three propaganda models.

This is all hence why “Black” is capitalized but “white” isn’t or why “white pride” is said to have hardly any meaning outside skin color or hatred. If any other trait that unifies Whites is searched for, they speak satirically of it, with examples such as Cracker Barrel, mayonnaise, Florida Man, or negatively as colonization and the like, or that classical figures having been White is irrelevant due to other scholars preserving their memory or their lineage not being able to be traced to present-day Whites.

I'm not sure why you're writing this. We are all aware of this propaganda. If you lurked our board more you'd know we've identified and discussed this hundreds of times.

In all, do any alt-right perspectives on these topics exist?

Yes. We identify it as one of many forms of Jewish subversion.

Here are some resources which illustrate the points made here.

We are already aware of these.