Might I posit that fandom - or anything else - is problematic when it becomes someone's entire existence, to the exclusion of everything else?

Yeah, I'd go with that. Fandom is, I think, a less socially-acceptable means of doing this than, say, being a partner in a law firm, but I'd say they're all problematic.

I don't think there's anything wrong with modelling on Captain Picard, because, as you said, you made a clear distinction between the fictional characters and the people you were working with. As I've said before, I think fiction does two things: it reminds you of things you knew already, and teaches you about things you didn't. It's not always reliable-- it comes through the author's interpretation, and s/he wasn't omniscient-- but if it shows you a model that works for you, why not use it?

Also, what's "Reining"? Like, horseback riding?

--R