Hello,
Thank you for reporting this.
About the order status:
1. You mentioned the seller dashboard. Is this question about WooCommerce or WC Marketplace?
2. To be clear, does the issue occur only when you apply coupons, or is it unrelated to coupons?
About the return statement:
By definition there can’t be anything after the return statement. It’s possible that I may have missed something, but why do you say that? What do you have in mind?
About the billing cryptocurrency field:
1. This entire plugin depends on this field so no, it cannot be removed.
2. You are right in that your theme doesn’t know about this field, so it will simply not display it. (It is still possible to display it using a hook if needed)
3. Removing the field will not solve anything
Please let me know about the questions on order status and also if you think something is missing from the checkout code.
I hope to investigate this early next week if all goes well.