[kh99]

For the title, the size of that field is coded in the newthread template (search for size="40"). The max chars in that field is set by the option for max thread title length in vBulletin Options.

For the message area, if you go to the Style Manager and pick "style vars" from the drop-down, there's one called "Message Area Width" that sets the width, but it does it for all of them and not just the new thread box, and you can specify a pixel width but I don't know how you'd do "the entire width of the browser". The actual box is in more than one template - two of them are named "editor_toolbar_on" and "editor_toolbar_off", so maybe you can change the html/css there to get what you want (again you'd be changing all message boxes).

Hope this helps.