1) You can see this in the task log (Status / Tasks then click Show Task Details and select tab Log).
In the beginning you will see two log rows like this:
(2015-04-23 08:45:16) Information: ClusterID=1
(2015-04-23 08:45:16) Information: QDSID=0b0f0342-6a53-e528-7376-185051f58f00
2) There is currently no way to pin a task to one specific distribution service. The one with the least load will be picked.