Is there a way to automatically suspend or cancel open orders once buying power drops below a certain level?
I know that certain conditions can be added to an order, but I don't see buying power as one of the available types: https://interactivebrokers.github.io/tws-api/order_conditions.html So this would mean that you have to write your own software to monitor the buying power and suspend/cancel open orders when so required.
To be honest, once your buying power is not sufficient to support your orders, they should be cancelled automatically unless they are reducing your position.