I could somewhat follow you until (3). Throwing the confidants and allies under the bus for idle public curiosity is absolutely not an acceptable trade-off.
If I dig in to the Saudi Arabia section of wikipedia I get to "Diplomats claim that Saudi Arabian donors are the main funders of non-governmental armed groups like Al-Qaeda, the Taliban and Lashkar-e-Taiba (LeT)". That is a quintessential staunch US ally. It probably is acceptable to throw them under a bus, metaphorically speaking and it is more useful than mere idle curiosity be useful to have that sort of information in the public discourse. The spending and liberty-backsliding done in the name of terrorism has been material to date.
It might help you to follow the perspective if you consider it is plausible that the US's current diplomatic strategy is ineffective and needs pressure to reform. Especially after discounting the heft of their domestic economy. From what I've seen of the game theory, generally speaking best policy is to be scrupulously open and honest with very short bursts of sudden backstabbing when it makes overwhelming sense. The is, happily, a strategy that is highly compatible with radically transparent democracy.
There isn't a way to run this sort of institution without transparency. The incentives don't tend to work out.
Lets pick on the one I think is easy here - a Taliban source. The US spent 20 years in Afghanistan, wasted trillions, murdered almost a million. Opportunity costs even bigger than the needless waste of course.
How much is that Taliban source worth vs. greater transparency that could have ended the war earlier? The biggest problem was publicising which interest groups in the US government were responsible for prolonging the inevitable. Just keeping all meeting minutes on a website unredacted would have been a lot more valuable than having a source.
The tricky one is the Saudis. How much is a Saudi source worth vs. full transparency of voters into the US-Saudi relationship? The issue here is ... we can't debate that, the necessary knowledge is secret. But since large organisations are generally dysfunctional, and there is no reason to believe that the Saudi source is more valuable than more transparency into what is actually going on in the Middle East.
The issue to me is that secrecy makes democratic institutions ungovernable - they can't be assessed without full information and therefore voters can't even attempt to make rational decisions. Full transparency is probably more valuable than the net influence of secret sources [0]. The value of long-term secret sources is highly questionable. If there is a source or confidant in some foreign organisation you want to protect, give them a passport and set them up in Texas. Problem solved.
It might help you to follow the perspective if you consider it is plausible that the US's current diplomatic strategy is ineffective and needs pressure to reform. Especially after discounting the heft of their domestic economy. From what I've seen of the game theory, generally speaking best policy is to be scrupulously open and honest with very short bursts of sudden backstabbing when it makes overwhelming sense. The is, happily, a strategy that is highly compatible with radically transparent democracy.
There isn't a way to run this sort of institution without transparency. The incentives don't tend to work out.