>In the age of Mao, wasn't it closer to Marxism?

Not really, marxism is a way of looking at the world, not an economic system in itself

>There are more billionaires in China now, then there were back then

They hadn't even built capitalism fully, so it makes sense that there was less capital

>By that I mean, the wealth disparity in China is at an all-time high now, is it not?

it is, and they're currently working on how to deal with that

>Xi keeps remove the 2 term limits from just position, and has been doing an excellent job at consolidating his power base, through all means necessary.

Sure, but that's just politics. Ultimately if the majority of the party had a problem with him he wouldn't be in power for long before a coup or a request for him to step down happened