"How long is long enough for that to lose its sting?" Frankly, Jack doesn't look old enough for the time that Gaeta would need to recover from that kind of betrayal to have elapsed. Maybe he's a more forgiving fellow.
He isn't going to touch anything having to do with sick human beings. Aliens? Aliens are safer. "What does your work entail? It doesn't sound like any service branch I've heard of."