Quick theory about Mike & Mona
This could be way off, but wouldn't it be a cool twist if Mona WAS planning to fake her death and Mike knew, and that's what they argued about the night before Thanksgiving. So she was collecting her blood and all of that in the previous few episodes. But then Mike talked her out of it and they made-up.
Then on Thanksgiving, she actually was killed, but Mike still thinks that she is alive and just changed her mind and ended up faking her death... which is part of why he wasn't so sad at first. Then he got really angry/sad not because she was dead, but b/c he thinks she lied to him about not faking her death and mad b/c she hasn't tried to contact him at all.
He could have been leaving the candy at a spot that had significance to them in hopes that he could get her to come out of hiding to meet him (but she doesn't ever show up there b/c she truly is dead).