shelleycat
hard to say exactly how much, just be sure to start out slow, like 1/2 cup a day. Some people get slight cramping as the mirobes go to work. Keep an eye on your tongue in case the dairy does turn mucous forming - it's unlikely, but still. :)
It's okay at any time before 8:00 pm, and in fact is possibly okay after 8:00 since fermented foods are pre-digested and don't require as much work from our enzymes.
I usually have goat kefir as part of my blueberry protein shakes. :)