I don't think you understand our constitution. You are correct that Mr. Obama's veto is ineffective given the margin the sanctions renewal act passed, which leaves him with only the choice of signing it within ten days as you say, or not signing it in which case...........it becomes the law in ten days, anyway. It's academic in any event. The new Congress and President will be in office next month and even if nothing happens until then, they would pass the same bill or an even tougher one, which President Trump would immediately sign. So, hardly, "poor Trump".
Our election is over. The nuclear deal is dead. Sanctions will be re-imposed. Nothing is going to change those things.