Those are very well made reactors, and it sounds like it has everything you need. To run it on your reefkeeper, you would need a solenoid (but that may well be included, if not it's not expensive). The reefkeeper will do everything a seperate PH controller will do. You can also run a reactor with no PH controller, but then you tend to have to do a lot of manual tweaking to keep the Co2 just right. Personally I much prefer to use a controller so I can basically set it and forget it. If you do use a controller, there are two ways to do it;
-One is to monitor the PH in the tank and have the Co2 shut off when the tank PH goes too low. Doing it like this, you will still need some peroidic tweaking of the Co2 flow as a lot of other vairables would affect the PH in the tank.
-The second approach is to put the PH probe directly in the reactor, or have the efflluent running into a small container and have the probe directly in that. This way you it is basically self adjusting, in that if you want to increase the effluent rate, the controller will adjust the Co2 for you automatically keeping the PH right where it should be so that the media dissolves at a deccent rate, but doesn't turn to gooo.
With Ca reactors, if you have them cranked up too high you will see increased precipitation on impellers and such, and you may cause sand to start to clump/turn into rock. You sort of can overdose, but the consequences would be nowhere as bad as if you say, way overdosed 2 part or even worse kalk. If you have a Ca reactor cranked up way too high, the first thing you would likely see is the PH in the tank being driven down.