Hi,
about question 1. check the documentation. I am not sure right now, but I think I remember that with predictive dialing a number set as primary number is used. (e.g. teh first number in the dataset)
I am not sure about 2. as well. Except for Preview dialer campaigns this is a quite unlikely situation. and with predictive dialer to work correctly you are blocked while in a campaign. But here as well check if there might be some not so obvious parameter. In predictive dialing this behavior avoids unpredictably "loosing" an agent the dialer took into account for dialing.
Number 3 will only work if you are doing campaigns out of SAP CRM and you might have access to what usually would be the campaign data for inbound here as well. Using only SAP Contact Center campaign data is a completely separate database, not related to any other customer data you might have in the SAP Contact Center (which actually might only be a directory entry)