Geralt notes that Odo's dog seems to be guarding something, but I can't figure out what any of that cutscene means. Is there any point to it?

Go back to that spot after sunset.

This is strange, now the dog isn't there anymore. Is this...good or bad?

There should be a short cutscene playing. If you didn't get it, it's probably too early. Do a few quests for 'main' villagers first.

And no, it's nothing terribly important, just one of small tidbits that add to solving the mystery of this area ;)

This is a piece of a little puzzle that will come together at the end of the chapter. I'll drop one hint for you: talk to old ladies, all of them.