1) Stevia. I’ve heard that some people use xylitol with no issues, but it seems to cause problems far more often than a pure form of stevia.
2) There’s a good list of die-off symptoms here: http://www.thecandidadiet.com/forum/yaf_postsm11590_Molybdenum-and-Dieoff-Symptoms.aspx#post11590
3) It’s possible. What are you taking for die-off? How much coconut oil do you usually consume in a day?