Yes, fungus does seem to act like an evil alien. It certainly wants to take everything over.
The pains I would get are mostly at the back of the head and top of the neck and mostly when I start to experience dieoff from either taking something anti-fungal or when I cut something out that is feeding the fungus. I take it to just be a symptom of the fungus getting a little angry and not getting what it wants.
Yes, the biotin is very safe. I was a bit hesitant at first and I slowly worked my way up to 10,000mcg per day. Once I hit 5000mcg I began to experience a lot of dieoff along with a dramatic improvement in digestion. Stomach started to get flatter as well. I just take 300mcg tablets and adjust accordingly.