On the topic of accidentally consuming something non-vegan (the lactose question). I agree with you :) veganism shouldn't be about 100% avoiding animal products at all cost - but simply living your life in a way that causes the least harm. I am vegan and have accidentally consumed dishes with fish sauce, honey, egg etc, and accidentally used products tested on animals. This does not make me any less vegan, I continue to strive to cause the least amount of harm I can.
This is exactly how I live. This is me right down to a tee. I try my best, I am not perfect, but I do the least harm possible for myself and 4 others. I don’t even label myself as vegan anymore because people go too far with it and it has tarnished the reputations of vegans.