> 1) How are broad secret court[4] and non-court[5] orders constitutional?
There are two broad concepts these rest on.
First, is that many of the NSA's activities do not require court oversight in the first place, because they rest on the executive's broad powers in foreign affairs. By and large, the Constitution does not apply on foreign soil, and so the NSA does not need a court order to spy on e.g. Angela Merkel. The crucial thing to understand about the FISA Court is that it's not an attempt to take something that previously required a warrant from a regular court and make it a secret proceeding. That would be unconstitutional. Instead, its an attempt to take a process that Constitutionally requires no court oversight and inject some court oversight to ensure that the NSA stays within its foreign mission.
The second broad principle is Smith v. Maryland plus the broad subpoena power. Smith v. Maryland says that information you put in the hands of a third party is not protected by the 4th amendment. The subpoena power says that you can always be compelled to turn over information pursuant to a valid investigation. The subpoena power is very old. It predates the Constitution by hundreds of years.
The anti-NSA side generally misunderstands the context of the 4th and 5th amendments. The background rule is that the government is entitled to evidence relevant to an investigation. Heck, even private litigants are so entitled. If you're suing a company, you can serve a subpoena on a third party obligating them to turn over documents relevant to the lawsuit. The 4th and 5th amendments are exceptions to those broad powers. And in an age where everyone's information is floating around in the "cloud" where third parties have access to it, Smith v. Maryland gives the NSA a very wide latitude in which they can operate and still in good faith say their programs are legal.