2. I wish I could give you that reassurance directly, but all we are really allowed to speak as people who might have access (members of the military, intelligence community, government, etc) to is what is already in the public sphere and, in many cases, not even to that. The particulars, though, would have been pretty closely held within the NSA, even if some of the broad outlines were more publicly available, because of the scrutiny with which any intelligence on American citizens receives. If you get Intel that mentions an American person, it never (in the general community, that I have seen) gives identifying information on that person. It will just say "An American Person vacationing in UngaBungaLand was contacted by WeHateAmericaYayJihad (WHAYJ) at grid coordinates xxxxx-xxxxx....", etc. Only those who were read in would have had the kind of access that is potentially worrisome.
3. I will say that the program gives me pause. It seems that unless protected by strong safeguards it could lend itself to incredible abuse. I think that the unwillingness on the part of Congress to take a more active role than that which was basically forced upon it by the Executive is more than lamentable, it is potentially dangerous.
4. That being said, I am not convinced that this program violates the Constitution - electronically it seems to be the equivalent of you writing a "To" and a "From" address on your mail envelope. Nobody at the NSA opens your mail unless you put the electronic equivalent of "Mr Gee Had, 911 Pakistan Lane" in your "To" block, or have it in the "From" block when you receive it.
The ability to open our mail (electronic, voice, physical, you name it) could lend itself to powerful abuse in the hands of unchecked actors. So can the ability to deploy the military, or federalize the National Guard. That is why I focus in on the degree to which these programs have oversight from all three branches of government.
and that's about the best I can do. It's not a panacea. It probably has helped save lives. It is probably also potentially dangerous - just like Government (like fire, a dangerous servant and a fearful master, as the man said).