1. i think the data services option controls EDGE(wap) and not edge(network signal) and it does not control the wifi(i think)
2. to determine if your phone is connceting from wifi or something else, EDGE will appear if you are using phone's internet. Wifi will appear if it's on and it shuold say T-mobile - "wireless network name"
3. if you cancel the email you can still access internet but from wifi only
4. yes it will but you will have to have the UMA option from T-mobile added on
5. if you are able to access the web and you haven't connected to a wifi access point, then i think you are using the phones internet...
If i am wrong in any of these responses, please correct me