Good questions Q1!
1. Sometimes "scare cards" are not scary, especially for high-handed readers who know they don't connect well with our range. So this is just a good general guideline and you are absolutely right that there are exceptions
2. Depending on whether we think our hand is good enough that if we bet and our opponent calls, we are likely to still get hand action. more worse. what better hands.
3. A larger size if coordinated can serve well as the flop. If you're unsure, choose 1/2 pot, which is usually a good default value.
For the quiz type questions at the end of your post, let me take a couple of these as examples.With TT as a set, he would check with 4 to a straight on the table and bet about 70% of the pot on the blank turn. With Rd8d I would bet both cards on the turn against most of the opponents, and reduce the size slightly to around 1/2 pot given this slightly drier board.
I hope it helps you!