Well, the population is now at 153 people and I'm still getting messages that some of my citizens fell in love. So if I put them in the church I'll have maybe over 160. Additionally, I have yet to put about 15 kids into school to become grown ups. Maybe I will test it until nothing will happen anymore. But then, 3 people of mine died forever, this could mean a few couples and kids less.
Ad 2. Can you give me a tip finding singers more effectivley? It's actually a bit short having only 2 ingame hours to search for singers every night (10am to midnight) and most of the time I just remeet people who've already sung their song to me (I collected about 15 songs so far).
To your question: Do you mean the races against the animals? If so, one of the animal is lingering in front of your castle. It is having a letter in its mouth. Talk to it and you can take the quest. When you beat it the next animal will be waiting.