I also think no. 1 will be the best idea. Time is crucial if we are to attack a fort so close to where other romans could be assembling. Waiting any longer would mean certain defeat, kidnapping Longinus would probably not achieve too much. So assaulting quickly before nearby romans can react seems like the only suitable alternative. It's interesting to reason about what the decapitated soldiers mean. Are the romans trying to make us lose discipline and attack in rage to fight a battle we can't win and take crucial losses, or a method of scaring us from attacking, because they in reality have a very small force inside the fort and expect to lose if attacked? I think the latter is more likely, because 200,000 romans wouldn't have enough reason to fear a 30,000 man large dacian force at Sarmizegetusa to think it necessary to try and get a crucial engagement here. Rather, I think it means they're too weak to withstand a proper assault launched quickly enough to not give time for romans nearby to come to their aid. And if we win here, we have the advantage of perhaps being able to block the Drobeta Danube crossing, which would be extremely good for delaying the romans, seeing as it's their best path for sending supplies to a roman army in dacian lands.