Hello toni.
1. It should work on multiple tills because it stores these values as ticket tags. If you can see these numbers under the ticket (yellow area) it should print well. The problem you are experienced might be different. I'll be happy if you can double check your rule and action configuration.
2. Can you give an example? What are the expected values if customer pays $10 cash and $10 CC for $20 ticket? What it displays now?
Footer note: I'm actively developing V3 features and these days I'm too busy to configure SambaPOS as you configured and testing it to see how it works. After weekend I hope I'll be able to find some more time for testing these.