What you can do is use the get_current_screen() function to get what screen the current user is on ( in the admin panel ) and only add those global values whenever the user is viewing the post page:
function my_format_TinyMCE( $in ) {
$screen = get_current_screen();
if( is_object( $screen ) && 'post' == $screen->post_type ) {
//styles for the editor to provide better visual representation.
$in['content_css'] = get_template_directory_uri() . "/build/styles/tiny-mce-editor.css";
$in['block_formats'] = "Paragraph=p; Heading 1=h1; Heading 2=h2";
$in['toolbar1'] = 'formatselect,bold,italic,underline,superscript,bullist,numlist,alignleft,aligncenter,alignright,link,unlink,spellchecker';
$in['toolbar2'] = '';
$in['toolbar3'] = '';
$in['toolbar4'] = '';
}
return $in;
}
add_filter( 'tiny_mce_before_init', 'my_format_TinyMCE' );