I'm going to play Devil's Advocate in order for you to up your budget...

No one wants to pay a lot for a bike. However, you want a light bike that can ride well in road, rain, AND on gravel and you don't like aluminum and also steel rusts.....which leaves carbon and titanium.

Based on your requirements, I would suggest either a carbon or a titanium Cyclocross bike with disc brakes. If this is going to be your "last" bike and you sound like you know what you like and what you don't like, I think that you should raise your budget quite a bit so that you can get exactly what you want in your "last" bike.