Hi,
1. 500 error.
Could you please try updating the plugin to the latest v2.5.0 (released just a couple of minutes ago)? Is the error still there? By the way, could you please let me know how many products do you have in your shop in total?
2. New orders status.
Generally, our plugin can change order status, not set the default order status. However, before I try to come up with some solution – the first thing that comes to mind – simply disable the “Processing order” email in “WooCommerce > Settings > Emails”. This will however will stop the email being sent when you’ll change the status to “processing” manually. To solve that, I would suggest creating some custom status (e.g. “In progress”) – for example with our Order Status for WooCommerce plugin – and using that instead of the standard WooCommerce “Processing” status. Hope you get the idea… Please let me know what you think.