Well, I think the alt-right has the same problem as BLM, and modern feminism. The term was applied, but the group does not have a clearly defined position.
Take Milo. He is Catholic, but not fundamentalist. Seems to be at least average if not above IQ (hard to tell with brits), not openly racist, does not seem anti-semitic ect. I would imagine he would be considered alt-right still, but he does not conform to many of your standards. It would be unfair to say you are wrong just based on that though, as we both agree there is an alt-right.
If you consider alt-right to be a pro-white religious sect of the right, then your argument fits. I think the problem with the term is that it also gets applied to people that are against "sjw". There does not seem to be an underlying theme in how the term is used, so anyone that is considered to be on the right can also be labeled as alt-right in different ways.
In your definition, those are things that I would agree would breed crazies. #1 alone is a huge factor in that context. I think what I disagree with is how the article framed the situation by comparing alt-right to Islamic terrorism as explained before. The context of "bigger" largely due to the fact that there are far more relative to population. Also consider that MLK Jr. was considered to be a large threat.
I think comparing the alt-right to the Nazis and putting people into gas chambers is very hyperbolic. Even if you are arguing that they appear to be on similar paths, the vast distance of racial nationalism to gassing Jews is so large that it strips away major parts that the Nazis represented.