Quitting would just be the first step in "I do not want to participate in this". Whistle blowing is much more complicated in that you are hoping to not just not be participating but maybe stopping it altogether. Being young and single compared to being older with dependents would absolutely make that decision harder. Violating secrecy laws to disclose illegal activity seems like something that should have a caveat to allow, but of course they don't.
Actually they do. The law states that not only is it illegal to classify stuff to hide illegal activity, things classified that way are not actually classified. The whistleblower before Manning was very careful about what they leaked, and apparently went through the right chains. He was found guilty of misusing government property and given a slap on the wrist... And blackballed from working anywhere they had reach. But the law itself upheld that what he leaked was not classified.
This is a moral psychological quandary: quit and hope everyone shares your moral compass. (hint: they don’t).
Or work to pressure change internally, and occupy space that might have gone to a more morally flexible person if it was made vacant; but while doing so engage in supporting immoral behaviour.
Neither work without organizing. You cannot apply any meaningful pressure from the inside as an individual worker. You also do not need to work someplace to organize it.
If you work outside of the organization and compel someone to act on your behalf, you will be charged with that. It's how journalists have been tripped up in the past. If someone leaks to a journo, the journo is not part of the leak. If the journo asks someone to get data to be leaked to them, they've overstepped and get into trouble. That's something to not be forgotten.
From the inside, talking to coworkers definitely seems risky. If they are not like minded, they could report you. It'd have been better to just have quit at that point.
Because of all of that, "ethical" leaking really does seem like the only option left. It's then a matter of can the leaker live with the consequences.