1 - 2) It is not supposed to retain that checkbox on editing the form. To make changes to the email settings, you need to edit the universal email server behavior that is added to the server behaviors panel.
3 - 4) Please provide more details.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.