Okay--so disclaimers up front: I don't make feta, I don't use raw milk, and I have only rarely used thermophilic cultures. From what I understand, however...
32 C is a pretty low temp for a thermo culture. Where'd your recipe come from? What I guess is going on is that your recipe was designed for a pasteurized milk. The low temp, therefore, requires that the acid develop for a long time (24 hours). When you follow the recipe with raw milk, all the native meso cultures, which are happier at 32 C, develop more rapidly and produce more acid than the thermo would by itself. This situation is exacerbated by allowing it to drain for 24 hours at room temperature (where the mesos continue to grow much more rapidly than the the thermo would by itself). That's my guess, anyway.
If that's right, you have a few options. Pastuerize your milk (kind of defeats the purpose of using raw milk) and follow the recipe as is. Continue using your milk and cut your 24 hours down to 12 (or even 6) and see how the cheese turns out. A potential problem with doing this is that the cheese might not drain enough (though, I think you'll be fine). You could try keeping the 24 hours but lowering the temperature of the room the cheese is draining in.
I personally don't see that using too much/too little rennet would cause your problem, but I could be wrong. Too much rennet, when using time to determine when to cut the curd (as opposed to the floc method), leads to higher moisture retention, providing more food for the cultures to turn into acid, which leads to overly acidic cheeses. I've only experienced overly acidic cheeses with aged cheese and most of those, I believe were not caused by too much moisture (which was a problem...) but because I let too much acid develop before I drained and salted the cheeses.
Hope that helps. Hopefully, too, if I've said anything too far off, someone will correct me.