I can't marry a single person. I've tried every console command I could find on the web to try and fix or reset the quest and all, and still nothing. People will comment on me wearing the Amulet of Mara, but I don't have the dialogue option to marry them.

You have to do their quest first; such as with Ysolda, you bring her a mammoth tusk. You should be able to marry all of your housecarls. After they comment on the amulet, are you clicking on the dialog "Are you interested?"