cancel subscription without cancelling card

Yes. Note that NS subscriptions are actually continuous, with monthly or yearly payment. With NS Flex subscriptions you pay per month and can change your subscription every month. I believe only the Dal Voordeel subscription where you travel on credit still has an annual payment, and this subscription can be ended after the first month.
 

Would i receive the rest of the 11months refunded?

Yes.
 

Does it refund to an Asian bank account ,or to the credit card that was used to purchase the subscription?

The refund is transferred to the account where the subscription costs are paid from.
 

Is it possible to terminate the subscription but still keep my ov chipkaart without blocking it?

Yes.
 

Cancellation of subscription can be done at any train station?

You need to cancel online, and confirm at a ticket machine.
 

There are ticketing machines at all ns train stations?

Yes.
 

Also i can't seem to add ov fiets onto my personal chipkaart. It never successfully logs in.

If you have an NS Flex subscription, then OV Fiets is automatically included. If you don't, then I would advise you to contact customer service directly to see what's wrong. Usually, this is most easily done by phone, as they are available 24/7 at 030-751 51 55. You may also contact them by chat (click the link Chat with NS on this page) or by sending a message on Twitter or Facebook.