I had the same problem, you go to your text messages, and the font is huge, so you pinch to zoom out and think everything is okay, only to go back and its huge again. Sooo..... go to settings/My device/Display/scroll to Font Size. Change to your preference there!
The solution is simple. The volume control keys are used to increase and decrease the font size. I'm not sure if that works anywhere else outside the messaging app.