Why didn't Ian just lie to Frank and say "I won't use it on Dan". Then, if things work out where both Dan and Danielle get saved, you use it. If they don't, then you don't use it and you've kept your word to Frank. Why is it so hard for him to lie to Frank? Frank is clueless about Ian though. He think he was pressured into things, not realizing that Ian hasn't been pressured into anything.