After much difficulty, I managed to use Amazon coins to buy card packs and get a 15-20% discount from buying it bulk. 

I still have quite a lot of amazon coins and my intention was to buy slowly as the new card pack offers from Blizzard came out. 

But it seems the amazon coins can only be used to buy the in game card packs, not the card pack offers from the Blizzard shop directly (i.e. it seems I cannot use my amazon coins to buy from Blizzard shop)

Is my understanding correct?

If so, is there anyway I can still utilise my existing amazon coins for any new card pack offers from Blizzard store directly?

I am loathe to charge money to my credit card again when I have quite a lot of unused amazon coins lying around in my amazon account.

Please advise me step by step.

On a separate note, because I did not start Hearthstone since its inception, I wanted to buy back one of the old adventures. (blackrock mountain) --I still do not have my Ragnaros and I am getting pelted everytime in Hearthstone by the fire god.

I realised I cannot use amazon coins to buy the old adventures too because they are found exclusively in Blizzard store? Is my understanding correct? Please also advise. Thanks a lot.