Is your $_Post returning the array as expected?
From what I’m seeing your add_action isn’t calling the right function either…
Either change wpprolister_ajax_layoutcontrol
in that line to ajax_layoutcontrol
or rename the function to wpprolister_ajax_layoutcontrol
Another option may be to put a selectbox meta on the page and use that to call the correct format though. then you don’t need to use POST data.
ie
function new_order() {
$template_check = get_post_meta( $post->ID, 'template_check', true );
get_template_part( 'content', $template_check );
}