Scenario:

I have 6 Amber in my pool, and 2 in my 'Safe Place'. Opponent player plays 'Burn the Stockpile' to attempt to force me to remove 4 of my 8 Amber. is the card null because I don't have enough Amber in my pool, or would I have to take 2 Amber out of my Safe Place, and remove 2 Amber from my pool?

You do not have 7 or more, nothing happens when Burn the Stockpile is played

You don't technically "have" the Æmber on Safe Place, so your opponent wouldn't be able to use this card against you.