Question #1
yes that is corect, you can go about this in 2 different way, either you get the Ex upgrade which alot more expension and barely cost a little bit more the redox card itself, the Ex will give 'Salinity, Redox, 3rd level port and 2 additional L port"

Question #2
If you want to have second Ph probe, there is 3 ways to go about this! You can get ph card only, Conductivity/PH card or Redox/PH card.
(Personally I did the ex upgrade and added a Redox/PH card also)

Question #3
The Simu-L will require 2 L port to run and 3 YL2-1 cable/spliter, for you T5 is 4 ballast total or 4 tubes, how many tube are going to have running?