On your Rule 1, do I understand that you can swap any number of letters on your turn before playing your word but with every 1-letter swap, the words need to remain valid? It's not good enough if you need to swap multiple letters before getting to a different valid word?
Correct. The goal is not really to change the words on the board, but rather to get better letters into your hand.
Think of it as "I would have a full word if only I could get [X letter]." You see [X letter] on the board, and you want it. You might have to do a chain of one-letter-at-a-time swaps though to get it. And each swap has to make a new valid word. But once you get it, you can play your bingo.
