As a non-native English speaker, the word "spiritual" continues to puzzle me, as I don't have a word to translate it to in my own language (Finnish). Or rather, I have two, so I wonder which one you have in mind, or is it maybe a combination of them, or something else?
I can think of "henkinen" which roughly has to do with cultivating your mind....that usually gets to be used in connection with stuff like literature, art, music. I guess doing aikido could be said to cultivate your mind in some ways. That wouldn't so much be anything that is explicitly taught in our dojo, more something that happens if you practice a while.
Then there's "hengellinen" which is a word used in context of religion, cultivating one's soul. I'd only use that word for dojo or people who combine their aikido practice with a religion (like shinto, I think some dojo do?). Our dojo doesn't.
There are some qualities that I think doing a martial art will help develop, like tenacity, mental toughness, patience, that kind of thing. Those to me don't quite fall under either category. And again, they're not something that is explicitly taught at our dojo, more something people develop (or not) as they progress.
As to the last question - I started aikido because it looked cool, and I wanted to learn how to fall.