Hi blackitnow!
1) It could be simple php script for traffic separation (I can post here code which divide the traffic into N equal parts).
2) The only parameter you should track is eCPM (Effective Cost Per Mille).
For example you have 2 campaigns: 1st $25 cpa and 2nd $35 cpa. You have send 15k to first and 30k to second. From each campaign you get 2 sales ($50 from first campaign and $70 from second). It's too hard to define which one is more profitable without eCPM.
Let's calculate it:
1st campaign -- 50/15000*1000 = 3.33
2nd campaign -- 70/30000*1000 = 2.33
So the first one is converting better, but the payout is smaller