Boethia can also get stuck in your journal if you accidentally read the book. I ran into it during the Vaermina quest (so there's no issue for your challenge), but I am sure that the book lies around in other places as well.
If you don't do the Vaermina quest, you cannot become the Thane of Dawnstar.
And the Clavicus Vile quest is forced upon you whenever you approach Falkreath once above level 10. A guard will walk towards you and force a dialogue onto you, concerning Lod and the dog. I think I avoided talking to Lod for several levels then ( = one less merchant to sell my stuff to), and the quest is now broken because the stupid dog won't even spawn.

You will also need to be always aware of the Vigilant of Stendarr in Markath, because he will also approach you if you come too close.
Oh, and there's a random encounter with an afflicted who will force the Peryite quest into your journal.
About avoiding the rumors topic with innkeepers... you can avoid them, yes. Unless you happen to want to cure your vampirism at some point, because I think that Falion will only be responsive after you've heard about him by some bartender.