1) on the admin_cms/contents_update.php and contents_insert.php pages, the wdith is set by the following line:
$CKEditor_config["width"] = "98%";
there is not a way to dynamically set this so you can have different widths for different content areas, but you can change the width globally by editing that line.
2 - 3 ) see the "Create New Pages from PowerCMS Templates" youtube video for details:
watch?v=kbplAlzNexI&list=PL21CA2EF37DE22B2C&index=2&feature=plpp_video