1) wow. your post has reminded me of just how versatile a cyclocross bike is. I commute on mine, do weekend road rides and a few multi day rides and occasionally take it onto gravelly trails. I haven't done any cyclocross races yet. but yeah, you can do all that stuff with one bike. maybe two sets of tires but yeah one bike. I used to work as a messenger and the general consensus downtown was that if we could only have one bike
2) I haven't ridden too many cyclocross bikes, but I am in love with my Giant TCX. It's roadbike light and very fast. But the angles are a little more relaxed. I picked it up used but in great condition with ultegra shifters and derailers, fsa gossamer cranks and easton vista wheels (they'll do for now) for $800. aside from the wheels, I can't imagine how this bike could be improved. You can get in the game for probably as little as $700 for a new bike, for something like a Kona Jake. Other people like steel bikes, like the Lemond poprad or the Bianchi Volpe (maybe a touring bike?) or the surly crosscheck. the crosscheck is often slighted for being heavy and sluggish, but it's an affordable complete build and the frame is versatile with horizontal dropouts.But no one is going to be able to tell you what kind of bike you're going to like. The important thing is to ride a bunch of bikes if you can in your price range and see what you like. the important thing after that is to ride it. and stay away from the internet, where people like me spend too much time writing about bikes and pretending they know what theyre talking about and dissecting bike parts and weight and overthinking everything instead of riding.