chewing gum

Question

Rabbi, I hope you don't mind me asking the following questions. I'm not questioning your authority or knowledge, but I'm a bit confused: I've read information about glicerin saying that some of it comes from animals, so therefore foods containing glicerin may be non-kosher (if the glicerin is not kosher). Why do you affirm otherwise, that all glicerin in food is kosher? Second, about gum base used in chewing gum: although it is not considered to be food, some of it usually does get digested, so if it is non-kosher, the body absorbs it. Finally, I found this ingredient in some chewing gums called Tartactic Acid, and I was wondering if there is any chance that it may be non-kosher (I read somewhere that it might be a problem). Sorry about these questions: I am just confused why different people have such complete opposite decisions about such important issues.