1. ECF Database itself currently does not support multiple stores, but the similar functionality can be implemented using different affiliate ids (used to access backend). Also each DNN site can connect to a different ECF backend by specifying different connection string and different affiliate id.
2. We did have an isue which has been addressed since, so you should be able to see prices now.
3. Yes ECF DNN uses SOA approach to connect to the backend and retrieve catalog/product and other information from using web services. No direct calls are made. For example ecf4dnn.demo.mediachase.com and ecf40.demo.mediachase.com are both driven by the same backend using web services. You can download a trial version of ECF and connect to the same demo backend from your side without need to setup any databases.
Hope this helps,
Sasha.