I went on and solved the remaining 8 puzzles in the game, as well as the 15 bonus puzzles I could now access from the main menu. This, of course, means that i decorated the inn rooms, and assembled the painting.
It took me 12 hours and 50 minutes to do all of this and finish the game. My final score is 5181 and i have 53 coins left. There are some weekly puzzles you can get by WiFi, but those do not count towards anything, so I will leave them for when I have nothing else to do. In any case, I think I can safely mark this one as 100% completed. There would of course be the ultimate option of starting a new game and getting the maximum score, but since the puzzles do not change, I see no point in doing this. I might try the sequel now, or maybe some other DS game.
As for the reader puzzles, I will put up answers tomorrow if no one solves them by then.