To answer one question, Tao and Dao are exactly the same. "Dao" is how they spelled it in the older system of translating Chinese (Wades-Giles), and "Tao" is the current way (pinyin). "Tao" is more accurate these days, but no one is wrong for using "Dao"; it's going to be found in older writings, so it will probably never go away. I lived in Beijing for 2years and learned Chinese kinda decently, so here are a few other bonus words that are exactly the same. In each example I'll put pinyin (the official modern way) first, and alternate older ways after:
qi = chi = energy (ki is Korean)
gong = kung
taijiquan = tai chi chuan = grand ultimate fist (most people leave off the quan/chuan; note "chi" is not the word "qi" in this phrase)
doufu = tofu (the food)
As for how I got to know Taoism, I was 18, across the country in Golden Gate Park at dawn, and saw a tiny guy in black doing taiji through the morning mist in front of the botanical gardens. It looked very much like the little guy at the top of this page! I watched from a distance and thought, "That looks like it feels good to do it". A few years later an opportunity came up to take an affordable 8 week class, and before long I was teaching that very same class! That was in the mid 90's, and I've been doing it and teaching it on & off ever since. Mostly "off" since covid started. Don't be impressed; time does not equal excellence, lol! I know a lot and have a lot to teach, but I lack discipline when it comes to myself.