I think the post about salt water is good. I remember my Mom making me gargle with salt water when I was sick as a child. It always made my sore throat better.
As far as the other questions, we can only speculate unfortunately. This therapy has only been studied by one published doctor, and that is in Russian. There are many things written about it, but they are all in foreign languages. We have been trying to get someone to translate a text we found, but it is in Urdu (we think). It's a mystery.
The people on this forum have come up with fantastic theories, just based on the properties of oil, and how oil affects your body. But in the end, we are all, as with many alternative practices, going based on how we feel, and what we see. The interesting thing about Oil Pulling is that for most, you see and feel almost immediate results from the beginning. That is almost unheard of in the alternative practices world. I think that is what hooks people, and keeps them doing the therapy.
It's strange how once you start, you simply cannot think of not doing it on a daily basis. It has many elements that are soothing, yet invigorating. It has an immediate effect on the health and feel of your gums, tongue and teeth.
I'm sorry we cannot answer your questions fully. I really wish we could. Perhaps someone will come along and post their theories. There are many hidden treasures in these 21 pages of forum, but it would take quite a bit of digging I'm afraid.