All antifungals promote digestion so if you take antifungals it’ll cause you go to the bathroom basically.
After consuming probiotics, you can feel a variety of symptoms so its hard to say whether its die-off or not.
The rash could be toxins being released from the body which are detoxed via the skin. Sometimes I get rashes from wanking it personally if I do it too much or hard, so it could be that but it doesn’t sound like it.
I wouldn’t worry about the lactose. Additionally I wouldn’t worry about your carb intake because you need carbs for energy and your general health.