1. Ba'athism is defined as "an Arab nationalist ideology that promotes the development and creation of a unified Arab state through the leadership of a vanguard party over a progressive revolutionary government". I don't want a progressive, secular, and communist ummah; I want a true Islamic empire that spans the globe. First we must start small though and try to unite the Arabs. If we can't even unite the Arab Muslim ummah, who've already had a history of trying to unite and already share an incredibly similar culture, how can we ever fathom an international Caliphate?
That's my entire reasoning behind that, sxb, it doesn't go deeper than that. I don't think Arabs are better than any other Muslim peoples, I just think it would be most convenient to start a future Caliphate from them.
2. You're definitely right that Arabs aren't the only people who've helped spread Islam, but most Islamic empires that have had the most historical impact were Arab (ex. Umayyads, Abbasids, Ayyubids, Mamluks, etc.). Not trying to diminish the importance of the many non-Arab Islamic empires, though. They were also great.
3. As Muslims, of course we're suppose to worship Allah but we're also responsible for helping out our fellow Muslims in need.