Talisman & Trapping the monsters

Let me preface this by saying I've seen a few comments on how the monsters were able to get into the barn at the scene everyone knows is too upsetting to talk about, but my question is how did they get out? Does the talisman only work to block monsters outside of a closed in area and not vice versa (i.e. keep them within an enclosed area)? Also we saw in tonight's episode that the monster said the talisman 'doesn't work that way' when Randall? waved it in their face, however they did not touch the talisman. Are they unable to physically come into contact with it? If so, it may explain why they did not take the talisman (assuming they left it alone) from the barn/destroy it. I think I heard the town's only got 12 talismans, but I may be wrong. I do not believe 12 is enough for everyone as we have quite a few people living solo it appears, or do they just have a never ending supply because the numbers aren't adding up in my head.

Also, in tonight's episode s3e4 why were they so concerned about boarding up the window when they have curtains? We saw in a previous season Fatima was able to use the talisman effectively with cloth