Hey Chris,
I rekon the Wigman and Midnight are on to it. Keep being clean and patient with the your kegged beer. Kegged beer always seems to taste better after 3-4 weeks under Co2, as opposed to the force carb and start drinking, I usually prescribe to. :chug: (carnt help me self sometimes)
Calculation of IBU with FWH? :blink: I FWH because it's easier, I add to FWH charge and then go mow the lawn or something for 90mins. All other hops go straight into the cube and dry hop. Not saying its the best method, just saying its easier.
I go off the BIABicus spreadsheet on BIABrewer website, to draft my recipes. But at the moment, I'm finding the best way to judge your bitterness is to keep records of additions, quantities, and tastes. once you get through a few cubes it'll get easier to dial in what hop levels you like to what ever beer your making. Use any software you like, treat it as a starting point and start experimenting :beerbang: