It is really rare for Salafis to identify themselves as "Wahhabis". You are right, non-Salafis may call Salafis "Wahhabis", even when they pray together in one mosque.
I agree that the Takfeer rules were pretty loose during Al Saud's expansion wars in the 1700s. That was generally made for political reasons. Apparently, Ibn Abdulwahhab himself didn’t care much about the bloodshed so long as this will lead to a “status quo” which few people will care how it came together. Otherwise, Sunni Salafis don’t consider non-Salafis to be non-Muslims. The proof of this is their intermarriage, and any daily prayer that takes place in any Riyadh mosque, where the number of non-Salafis can exceed % 30 of those who perform the prayer.
You can go wrong about Salafis, but you will never be wrong about one thing, their complete lack of tolerance towards Shiasim. Once again, the finger prints of Ibn Taymiyah are found. If I can judge, I would say that among all of his writings, Ibn Taymiyah’s harshness against Shiasim was unmatched by any other religious groups he criticized. All that can be found in his book “Minhaj Asunah Annabawyyah "منهاج السنة النبوية”. He wrote it in response to Al Hilly’s book “Minhaj AlKaramah "منهاج الكرامة". Virtually, all of the current Salafi & Sunni arguments against Shiasim was taken from the strong critique of Ibn Taymiyah he summrized in the aforesaid book.
Well, that's mostly right. Ibn Taymiyah, like Allamah Hilli, was more of a scholastic person, while Ibn Abdul-wahab was a more pragmatist person, that's what distinguishes Ibn Abdul-Wahab. I do believe that his radical thoughts about shrines and shias, was a tool to allow his followers to plunder shrines, since shrines, specially Karbala, were very wealthy, and had a big amount of gold, ... About Takfir, it is said that they consider non-Hanbalis as kafir, although some say that they have historically fought with the pretext of kufr against non-wahabi hanbalis as well. Anyway, it is a dangerous cult, and needs to be controlled, otherwise, it would defame muslims and arabs.