When you are testing in the sandbox you should have all the details you need to perform the test with your test user. If you do not see a cvv value then you should be ok to enter any one that you want.
I think the real key to the issues you are experiencing is this one:
This transaction cannot be processed due to an invalid merchant configuration
All of the others seem to be specific to the way that you are entering the credit card info. This error is different though, it is saying that the merchant is not configured to be able to make this type of transaction. If you are getting this with your SandBox test then the sandbox merchant might need to update their profile to either agree to the new billing terms, or sign up for Payments Pro specifically.
I think once you got past this issue you would see that the short error messages are pretty descriptive about the problem. You can either put in some notes on your checkout form, or you can add in some server side validations to the form to catch this before it goes through the checkout.