Hi Alex,
To answer you 2nd question,
Please visit : https://docs.mendix.com/howto/logic-business-rules/set-up-error-handling
See Custom without rollback or Continue in error hanling.
For your 1st it depends on your authentication to use your certificates, like you mentioned token – I usually have REST API calls without certificate and uses only token via refresh or JWT.
So please try different ways by deleting the certificate and try only with Token.
If you use expired certificates, Mendix won’t let you go forward.
Hope answered your question,
Ashok