Re. not saving the ingredient measurements when adding a new recipe: I've checked now and it is because I added custom units. As they've been stored in the db options with carriage returns as the separator and update_post_meta() doesn't do any trimming, they don't subsequently match any of themselves again.
In meta_box.php, I've changed:
if ($new && $new != $old) {
update_post_meta($post_id, $field['id'], $new);
to quickly trim measurements:
if ($new && $new != $old) {
if ('ingredient' == $field['id']) foreach ($new as &$ingredient) $ingredient['measurement'] = rtrim($ingredient['measurement']);
update_post_meta($post_id, $field['id'], $new);
but it'd probably be better handled when saving the custom units initially.
Also, http://wordpress.org/extend/plugins/lightbox-plus/ has been working very nicely with the instruction images - I can now flip through a mini gallery of full size photos per recipe. Now I just need to take better photos :)