Is this imperialism by China, a country which is supposed to be left-wing? Leftists are normally anti-imperialism. Wouldn't it be better to let Taiwan democratically decide whether they want to be part of China or not?
8% of the total population is far from representing the working class, let alone being led by them.
Yup, it can and it should be much larger. I saw a chart showing membership growth of 2-3% per year. That said even at the present numbers it means every third family or so has a party member.
Again, China isn't calling itself communist. And I don't think they're. That said capital is subordinate to state control, which is subordinate to an org that most people can participate in, so personally I grant them the socialist (market economy) label that they tend to use. But I do understand why not everyone does.
To be clear, if you're not communist, it doesn't mean you're capitalist. There's a lot in between and it's often a matter of degree of one thing or another. Feudalism didn't turn into capitalism the moment the fist capitalist firm formed. It transitioned to capitalism as more and more production became capitalist, at some point becoming the dominant mode of production.