as far as an act 3 ticket goes, does that include the shared storage, or is there another item i need? Is the act 3 ticket worth it?

Well considering the act 3 ticket is required to do anything beyond act 2 I would say yes it's worth it. However no it does not unlock the shared stash or extra storage. As far as I know there currently is no way to unlock the shared storage.

What this guy said is all true. The shared stash is not accessible as of now. The act 3 ticket is of course worth the money if you wish to continue playing the game as it gives you act 3,4,5 plus access to stonehenge, 2nd attack and the Abyss.

so the $4 ticket gives me access to all of that with just one purchase, or per character?

Once you have purchased the ticket and used it, all the characters on your account will have access to the content.