I do not think a peristaltic pump would work very well since it is not designed to have very precise volume control. I have a new syringe pump design that does not require 3D printing. It uses the linear actuator kit from Open Builds (http://openbuildspartstore.com/c-beam-linear-actuator-bundle/) You also need a NEMA 23 motor, so the actuator will run about $120 USD.
The pH probe is from Vernier Instruments and cost about $80 USD. It is a pretty good deal. To connect the probe, you need a BTA connector, which you can get from Sparkfun. The probe requires DC power and ground and outputs an analog voltage. I have a circuit board that we designed for this and I can figure out a way to get you one if you want.
I don't know why your computer is freezing up when you try to run the GUI. Perhaps the 32 bit exe file will not run on your 64 bit computer. If you download all the pde files, you should be able to compile the program and export a 64 bit exe program (or you could just run it from the Processing program). To do that you will need to download the most recent version of Processing from processing.org.
I will be happy to help if you decide to pursue this and run into difficulties. You can contact me direct at the following: summers at wcu dot edu,