Phase 2 projected service at Birmingham Interchange is 2tph Birmingham, 1tph Manchester, 1tph Scotland and 1tph Leeds. However, once you build the station, there's no reason why you can't stop whatever services you want there. As with all of Phase 1, the benefits of the infrastructure built increase as more and more high speed track is built around the country. Also, the high speed and classic stations are linked by a people mover, authorised by the same Hybrid Bill and built at the same time as the HS2 works, so the actual distance between the two is not that important. In future, once you have fast services to Scotland stopping there, the few minutes you would spend in a people mover vehicle to get from one to another is going to be as meaningless as the few minutes you would spend on an airport's people mover system when you're going to fly significant distances around the world.
When you take into account walking time from platform to the "people mover" (any transport vehicle is a "people mover":roll and then at the other end plus with some of the services listed being only hourly you are looking at 30-80 minutes connection - not meaningless at all. How fast and how much capacity will it have? If it is like the current airport fenicular, then you could be in a queue for a long time.
No, they would stop at the major WCML fast stations like Rugby, Milton Keynes and Watford, not some of the suburban ones like Hemel Hempstead. As I said, we don't know the specifics of what service operators would exist on the post-HS2 WCML so we can't assume that there would be a clear demarcation in service quality between the 'commuter' WCML fast services and long distance ones, especially when Chester/North Wales and Stoke will almost certainly end up served primarily by HS2 classic-compatibles.