My guess is that your experience with kefir is the same as mine with cultured vegetables (see my thread of a few days ago). I have concluded that it my allergy to yeast that is the problem. That you react strongly to kefir grains and also have problems with Threelac and sauerkraut supports this.
I suggest you try making kefir with a starter culture that doesn't contain any yeasts. You could also try making young coconut kefir. It seems like you had some benefits from drinking kefir so I wouldn't abandon it completely.