That'd be pretty surprising that you can't stop email from automatically coming to the device.
Playing around with the simulator, what's the option to Send Email to Handheld (Yes/No) in the email settings?
Since the hosted exchange service has IMAP access, I couldn't just create the account as an IMAP type account as opposed to using the service's blackberry connectivity option?
The simulator also answered question 3 with a Yes. I see there's a simple option for 1x only.