Meta boxes not saving

I believe the issue is this line:

     if( $post->post_type == 'startups' ) return;

Won’t your custom posts always have the type startups? Basically you are telling your code that whenever I save my custom post type, ignore my custom fields. You probably meant to have one of the WP reserved types (e.g. revision or attachment) that would prevent your meta data from being overwritten in inconvenient ways.

I would change that line to

     if( $post->post_type == 'revision' ) return;

Or you could remove that line entirely (for testing purposes).