solved with fjk87 and http://tracking202.com/videos/. please delete
1) Your clicks get unique identifying 'codes' by using sub ids generated by the tracker. You can add / remove converting sub ids manually and it makes it easier to identify networks losing clicks / similiar stuff. From what I know not all offers require you to do it, but I'd highly recommend it. It does not require any additional work from your side.
2) You're talking about a simple landing page? If so, you put the link for the LP shown in prosper for every link you want to be outbound. Post a screenshot or hit me up on skype if you need help on this as I don't have prosper installed anymore.
3) The pixel should fire anyway (anybody correct me if I am wrong). It's placed on the final page of the paid action, therefore should fire if the process is done, not depending on the sub id.