"Ya know" or "y'know" is, as you guessed, the written version of when we say "you know" in conversation.
Propaganda is a message or information given specifically for the reason of influencing someone's opinion. Instead of giving straight-forward, balanced information, the information is slanted to support a particular viewpoint.
In the US, we refer to it as "scraping the bottom of the barrel" or "he had to scrape the bottom of the barrel." This means that you're down to your absolute last resort; you have no other choice. (For example, if you've asked five different girls to go to the school dance with you, and they've all refused, and you end up taking your cousin, you're scraping the bottom of the barrel.) (No offense meant, I'm sure your cousins are lovely girls!)