I have a passe ND that I purchased in 2015. Is that still valid to only be recharged?
Upon arrival at CDG, do I need to go to the ticket office to recharge or can I recharge using an American chip credit card at the billetterie machines at airport?

Since the ND ends on Sunday at midnight, and I'm taking RER back to CDG on Monday morning, what is the suggestion for this return ticket to CDG? Maybe buy a one way 10€ ticket to CDG? And is it best to do this at CDG on the day that I arrive Paris, or is it easy to get from any of the Paris metro stations? A ticket counter or a ticket machine?
If so, do I need exact cash or can I use credit card?

Thanks.