Thanks for your interest in Exchange and the Membership add-on. Hopefully I can answer all of your questions.
- There isn't an option to restrict access based on IP address.
- When a customer views content they don't have access to, there isn't an error page, just the restricted content message.
- This isn't an option in Recurring Payments at this time. It has been added as a feature request which you can vote for on the Exchange Roadmap, but I don't have a timeline for if/when this will added.
- There isn't a way to create a custom restricted content message based on membership level. You can, however, use the excerpt option and create a custom excerpt with a message stating what membership level is required.
- This isn't an option at this time, but I do think it's a great idea and have added it to the Roadmap.
Let us know if you have any additional questions.