The most efficient depends on your personal case, and the two resources only you can judge: time and money. Feasible is two RTs in PE to AMS for a week (say T-W) with a weekend trip in J to KRK.
Don't cancel your dutch Amex. Keep your dutch bank account open and, when the time comes, go through the suffering to reach someone on the phone and change the address manually.
I don't know whether bank bonuses stack, but you could try.

Calculate the cost honestly. FB platinum only really helps for international travel out of the US. After a few trips through the border, you'll have a better idea which way things are going, and how often you'll be flying.

And remember, report any assaults to the detainment staff immediately. Door!