"how to... test those waters in my newer relationships"
That's been a tough one for me. I think the hardest part is realising a lot of people just don't want to--or even know how to--have those conversations. I've been so lucky to know people (like you and R, and many more over the years) who love digging into abstract ideas. But some of the people I like best don't think about the world in the abstract--like, ever. And that is totally ok! I don't think it makes them superficial; our perceptions of the world are different. But I can't help feeling sort of lonely.

"(Usually, by the time I reach that point, the conversation is over.)" Hahaha, so much yes.