You are his anchor to Indiana. But honey, that doesn't mean you can't sail the waters. You said he has never made the effort to come back to Indiana to visit you, but he calls you and e-mails you regularly. Many adults feel they can't be just friends with the opposite sex, when that just isn't true. And it seems you are now just friends with Bill.
Relationships change over time.
If you feel you'd like to keep your friendship with Bill, keep it. There is nothing like a good friend. Start dating, if only to find out how wonderful it can be, to be treated as a significant other in a relationship. But when you find that special someone, you'll know it. You won't want to be that far away from his arms for long.