things i don't get, spoilers, and questions

1- wouldn't joanna have known that don would recognize that her handwriting didn't match sonny's? the first letter might have been typed, but the second was a postcard.
2- if she's so good at research, why didn't she know sonny was dead?
3- regardless of whether or not the "roast" was otis' foot (as someone suggested), how did she not know price was dead, since his body was in the freezer where the "roast" came from?
4- all the lying confused me. was there or was there not a secret inheritance, and whose was it, don's or price's?

btw, i thought elisabeth's performance in the final confrontation was hilarious. "don, kill him, we'll split the money. No? ok, mel, you kill don, we'll split the money." i had to watch that a couple of times.