The whole hot water/cold water opening/closing pores thing is a myth. They stay the same size unless they are filled (i.e. always the same size unless you get a blackhead that will push them open).

Best advice is samples! Go to a beauty clinic/chemist and get different samples and give them ago. Once you find the right product voila. It took me years to find my current moisturiser, I had tried so many but I always found that I had lots of pimples even when using things designed for oily skin. My beauty therapist gave me samples and I found the perfect product :)

my mom has very sensitive skin too... it goes red and splotchy quickly if something 'not allowed' even touches her face. She uses the beauticontrol line.