So I called AMEX To Find Out
Seeing as there was confusion on the thread I called OPEN Plat cust service and asked. The gentleman seemed knowledgeable and told me:
a) The spending is either across your OPEN or your personal, not combined. He said that once in a blue moon (his words, not mine) if someone is real close on OPEN and spends a good deal on personal they will give it to you.
b) He also said that the OPEN spending requirement was recently raised to $350,000.
Can anyone confirm b ?