And wouldn't that make both him and you unhappy?

I believe that that is exactly what people mean when they say settle in this manner--they mean they can't get who they really wanted. So yes, they're unhappy and they make you unhappy.

All this talk about how you (global, not specific) would rather be alone than with someone not right for you is hooey. It's hooey because it's just dramatic, over-the-top, meaningless prattle because how many would actually choose to be with someone they don't really want? It's a great sound bite, I guess, but everybody pretty much understands that they want the right person, not just any person.

Though, I do remember having a "pact" with someone back in my 20's and we said that if we weren't married by 40 or something we'd marry each other. Thankfully, we never had to honor that pact.