I believe you can hide the edit tab with CSS. You can add this to your form settings so it only occurs when the form is open. And do this with care, removing the wrong area or too much of the ribbon can have odd effects.
Yes, it will be for the whole form.
is the class selector that is already on the page, and
is the style to that will be set on a match if found
Test this on a dev box first to make sure it has the effects your looking for.