Hokkien and Min Nan are more or less the same language. If you really want to group it, then Hokkien is the mainstream form of Southern Min (Min Nan), not the other way round. https://en.wikipedia.org/wiki/Hokkien
97% of the people of Taiwan don't agree with you. And historically, Taiwan was part of China for four years (1945-49). And that only because of an invasion of a million-man army. In the 19th century, Taiwan was part of the Manchu empire, not the Chinese empire. Actually Taiwan was controlled by the Portuguese and Dutch before the Chinese arrived. Maybe it should be given back to the Dutch?
This is just a ridiculously unrealistic claim of a dictatorship. Taiwan meets all international law criteria for sovereign states (check "Sovereign state" on Wikipedia to verify). Even from 1945-49, the mainland, as well as Taiwan, were part of the Republic of China and not the People's Republic, which was only proclaimed in 1949, meaning that Taiwan was never under the sovereignty of the People's Republic of China. Under international law, the claims are based on a completely abstract and controversial subsequent unilateral revision of the treaties with Japan. However, the reality is different and China's claims are insubstantial and purely politically and strategically motivated.