I have the same system. As for using the PH Controller, you could, but it's a major waste of money imo.
I got the same regulator about a year ago, and have never used any probes. I just throw the C02 in through a reactor (currently a power head, not the best, but works very well!!), and use a bubble counter with a fine needle valve. To start off, set it to around 1 bubble per second or less, and measure your PH and KH until you get to around 25-35 ppm. Do things slowly though threw out the day. Once set up, you should never have to measure it again. Check it for a couple of weeks though just to make sure things are steady.
To answer your question about the controler though, it stops at what ever PH you set it to. Lets say a KH of 11 and a PH of 6.8 get you a total C02 concentration of 30 ppm. You would then set the controler to a PH of 6.8. The controler then would stop and go to keep the PH steady at 6.8. Once it hits 6.8, it turns the C02 valve off. When it goes lower, it turns back on. It works, but is really not worth the extra 100 hundred or what ever. You better off investing in a good reactor, wheter it be DIY or store bought. The reactor can make all the difference.
As for other equipment effecting the controller, not rue at all. Ive seen them run on systems with several other equipemnts plugged in along with them.
