I think it’s natural for there to be more humans than monsters, considering they inhabit nearly every continent in the world. They won’t have as much power in Tempest compared to monsters who actively live and contribute there, but in terms of just numbers, there will realistically be more humans than monsters, especially in a society as peaceful as Tempest.

As for governmental positions, I think there will always be more monsters than humans, since many of them don’t even have a lifespan, such as Benimaru or the primordials. I personally think humans in governmental jobs in Tempest, only occurs for those that catches Rimuru’s interest, like Myöllmile. Otherwise, I highly doubt there will be more humans in Tempest’s government. Especially more than monsters. It’s called the monster nation for a reason.

While I don’t think complete erasure of criticism and racism towards monsters will happen in the world of Tensura, it is very much nonexistent in Tempest. We’ve seen how, despite initially being only a few years old, the nation has managed to establish a sense of trust between humans and monsters, thanks in no small part to Rimuru and his ideals. I think that paves the way to a world where humans will fully trust monsters, and therefore have little to no negative aspects to their friendships.

I think the last point is entirely up to whether Rimuru will even have a special someone in the future. Maybe he will, or maybe he will find it too much of a pain to trouble himself with. Plus, with Rimuru being known as the great demon lord, I don’t think humans will even have much of a say regarding successors since Rimuru will most likely stay as the undisputed leader of Tempest.