It seems to me that you're wondering if you should make a move or not on your sexy professor, and you want to know how.
Lets get past the first part of you're question, should you? Well you say he was being friendly and open and forward, but you found nothing concrete.
But then again he didn't have to be so warm, and then again he's white so you don't know if you're "misreading" him and blah blah blah blah blah.
I Didn't Know That This Happened to Grownups
I didn't know this kind of stuff happened with full fledged grownups, why don't you send him a note: "if you like me check box 1..." but seriously, the only person who can really tell if he was receptive to you as far as flirting goes is you.
Trust your gut, does it feel like he was? But then again he could be that nice to everyone. Have you ever tried observing him with other students to find out how he acts toward them?
You Have Nothing to Lose
So to answer the first part of your question: you have nothing to lose if you go for it... and when I say "go for it" I don't mean jump all over him or anything, just try to get to know him better, try to become his friend, try to spend more time with him, corner him after class visit his office a lot. Anything just to get to know him.
The key word is "subtle". This subtle approach works because if you find out he has a wife or he's gay or he's in some other type of romantic relationship or just plain not interested, you'll merely look like a dedicated student. If, however, while spending more time with him and feeling him out with your intuition, you find that he IS interested, then, hey, there's the green light
What Are You Afraid Of?
There's only one thing that concerned me about your letter, you said that when the conversation started getting personal, that coupled with the fact that you had somewhere to be led you to leave. If you really want to get to know someone why should you be afraid of "getting personal"?
Your concerns are very justifiable but you have an advantage that I don't yet have: you can tell the boy you like that you like him without him giggling and running out and telling all his friends.
You're grown up, act like it.