spam will probably continue because as you block one based on it's email address, the same message comes to you with a different email address.
if you are confident every one who is going to email you has your email address, set the filter, i assume yahoo has a spam filter higher then you have it now.
before you clear out your junk mail folder, you wil want to scan through the messages andif you find it is from someone you want email from, mark it not junk.
i am using the only terms i know, because i use hotmail, and i have found it will filter some of the guys emails into the junk mail folder. the hotmail filter does screen most spam quite well.
as far as the misspelled words and all the other wierd stuff, i too will look for someone else to give us both an idea why.