Caso, sorry, I can't really answer, but I have read elsewhere that those seemingly useless tasks seem to help the villagers later on....ie they seem to rejuvenate better after a few distractions. I usually let them wander off and do what they want.....as long as they come back to what I want them to do afterwards.

I can't remember what puzzle 7 is off hand....my palm is downstairs at the moment, but it sounds like you are doing fine. The remaining puzzles will be solved when the right conditions are met.....whether you need to do more, or the game chooses the timing, is for you to find out
